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Lamp G, Sola Molina RM, Hugrass L, Beaton R, Crewther D, Crewther SG. Kinematic Studies of the Go/No-Go Task as a Dynamic Sensorimotor Inhibition Task for Assessment of Motor and Executive Function in Stroke Patients: An Exploratory Study in a Neurotypical Sample. Brain Sci 2022; 12:1581. [PMID: 36421905 PMCID: PMC9688448 DOI: 10.3390/brainsci12111581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/25/2022] [Accepted: 11/12/2022] [Indexed: 08/30/2023] Open
Abstract
Inhibition of reaching and grasping actions as an element of cognitive control and executive function is a vital component of sensorimotor behaviour that is often impaired in patients who have lost sensorimotor function following a stroke. To date, there are few kinematic studies detailing the fine spatial and temporal upper limb movements associated with the millisecond temporal trajectory of correct and incorrect responses to visually driven Go/No-Go reaching and grasping tasks. Therefore, we aimed to refine the behavioural measurement of correct and incorrect inhibitory motor responses in a Go/No-Go task for future quantification and personalized rehabilitation in older populations and those with acquired motor disorders, such as stroke. An exploratory study mapping the kinematic profiles of hand movements in neurotypical participants utilizing such a task was conducted using high-speed biological motion capture cameras, revealing both within and between subject differences in a sample of healthy participants. These kinematic profiles and differences are discussed in the context of better assessment of sensorimotor function impairment in stroke survivors.
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Affiliation(s)
- Gemma Lamp
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC 3086, Australia
| | - Rosa Maria Sola Molina
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC 3086, Australia
| | - Laila Hugrass
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC 3086, Australia
| | - Russell Beaton
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC 3086, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, VIC 3022, Australia
| | - Sheila Gillard Crewther
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC 3086, Australia
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, VIC 3022, Australia
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Spiteri S, Crewther D. Neural Mechanisms of Visual Motion Anomalies in Autism: A Two-Decade Update and Novel Aetiology. Front Neurosci 2021; 15:756841. [PMID: 34790092 PMCID: PMC8591069 DOI: 10.3389/fnins.2021.756841] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
The 21st century has seen dramatic changes in our understanding of the visual physio-perceptual anomalies of autism and also in the structure and development of the primate visual system. This review covers the past 20 years of research into motion perceptual/dorsal stream anomalies in autism, as well as new understanding of the development of primate vision. The convergence of this literature allows a novel developmental hypothesis to explain the physiological and perceptual differences of the broad autistic spectrum. Central to these observations is the development of motion areas MT+, the seat of the dorsal cortical stream, central area of pre-attentional processing as well as being an anchor of binocular vision for 3D action. Such development normally occurs via a transfer of thalamic drive from the inferior pulvinar → MT to the anatomically stronger but later-developing LGN → V1 → MT connection. We propose that autistic variation arises from a slowing in the normal developmental attenuation of the pulvinar → MT pathway. We suggest that this is caused by a hyperactive amygdala → thalamic reticular nucleus circuit increasing activity in the PIm → MT via response gain modulation of the pulvinar and hence altering synaptic competition in area MT. We explore the probable timing of transfer in dominance of human MT from pulvinar to LGN/V1 driving circuitry and discuss the implications of the main hypothesis.
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Affiliation(s)
- Samuel Spiteri
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, VIC, Australia
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Mu E, Crewther D. Nonlinear VEP: Facial emotional information is present in early V1 processing. J Vis 2020. [DOI: 10.1167/jov.20.11.624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Mu E, Crewther D. Occipital Magnocellular VEP Non-linearities Show a Short Latency Interaction Between Contrast and Facial Emotion. Front Hum Neurosci 2020; 14:268. [PMID: 32754021 PMCID: PMC7381315 DOI: 10.3389/fnhum.2020.00268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 06/15/2020] [Indexed: 01/13/2023] Open
Abstract
The magnocellular system has been implicated in the rapid processing of facial emotions, such as fear. Of the various anatomical possibilities, the retino-colliculo-pulvinar route to the amygdala is currently favored. However, it is not clear whether and when amygdala arousal activates the primary visual cortex (V1). Non-linear visual evoked potentials provide a well-accepted technique for examining temporal processing in the magnocellular and parvocellular pathways in the visual cortex. Here, we investigated the relationship between facial emotion processing and the separable magnocellular (K2.1) and parvocellular (K2.2) components of the second-order non-linear multifocal visual evoked potential responses recorded from the occipital scalp (OZ). Stimuli comprised pseudorandom brightening/darkening of fearful, happy, neutral faces (or no face) with surround patches decorrelated from the central face-bearing patch. For the central patch, the spatial contrast of the faces was 30% while the modulation of the per-pixel brightening/darkening was uniformly 10% or 70%. From 14 neurotypical young adults, we found a significant interaction between emotion and contrast in the magnocellularly driven K2.1 peak amplitudes, with greater K2.1 amplitudes for fearful (vs. happy) faces at 70% temporal contrast condition. Taken together, our findings suggest that facial emotional information is present in early V1 processing as conveyed by the M pathway, and more activated for fearful as opposed to happy and neutral faces. An explanation is offered in terms of the contest between feedback and response gain modulation models.
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Affiliation(s)
- Eveline Mu
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, VIC, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, VIC, Australia
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Ciorciari J, Gountas J, Johnston P, Crewther D, Hughes M. A Neuroimaging Study of Personality Traits and Self-Reflection. Behav Sci (Basel) 2019; 9:bs9110112. [PMID: 31694206 PMCID: PMC6912258 DOI: 10.3390/bs9110112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/01/2019] [Accepted: 11/02/2019] [Indexed: 12/01/2022] Open
Abstract
This study examines the blood-oxygen level dependent (BOLD) activation of the brain associated with the four distinctive thinking styles associated with the four personality orientations of the Gountas Personality Orientations (GPO) survey: Emotion/Feeling-Action, Material/Pragmatic, Intuitive/Imaginative, and Thinking/Logical. The theoretical postulation is that each of the four personality orientations has a dominant (primary) thinking style and a shadow (secondary) thinking style/trait. The participants (N = 40) were initially surveyed to determine their dominant (primary) and secondary thinking styles. Based on participant responses, equal numbers of each dominant thinking style were selected for neuroimaging using a unique fMRI cognitive activation paradigm. The neuroimaging data support the general theoretical hypothesis of the existence of four different BOLD activation patterns, associated with each of the four thinking styles. The fMRI data analysis suggests that each thinking style may have its own cognitive activation system, involving the frontal ventromedial, posterior medial, parietal, motor, and orbitofrontal cortex. The data also suggest that there is a left hemisphere relationship for the Material/Pragmatic and Thinking/Logical styles and a right activation relationship for Emotional/Feeling and Intuitive/Imaginative styles. Additionally, the unique self-reflection paradigm demonstrated that perception of self or self-image, may be influenced by personality type; a finding of potentially far-reaching implications.
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Affiliation(s)
- Joseph Ciorciari
- Department of Psychological Sciences, Centre for Mental Health, Swinburne University of Technology, Melbourne 3122, Australia;
- Correspondence:
| | - John Gountas
- Department of Psychological Sciences, Adjunct, Swinburne University of Technology and Department of Marketing, Adjunct University of Notre Dame Western Australia, Fremantle 6959, Australia;
| | - Patrick Johnston
- Faculty of Health, School of Psychology and Counselling, Queensland University of Technology, Brisbane 4000, Australia;
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne 3122, Australia;
| | - Matthew Hughes
- Department of Psychological Sciences, Centre for Mental Health, Swinburne University of Technology, Melbourne 3122, Australia;
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Shiferaw B, Crewther D, Downey LA. Gaze Entropy Measures Reveal Alcohol-Induced Visual Scanning Impairment During Ascending and Descending Phases of Intoxication. J Stud Alcohol Drugs 2019. [DOI: 10.15288/jsad.2019.80.236] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Brook Shiferaw
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
| | - Luke A. Downey
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
- Institute for Breathing and Sleep, Austin Hospital, Melbourne, Australia
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Shiferaw B, Crewther D, Downey LA. Gaze Entropy Measures Reveal Alcohol-Induced Visual Scanning Impairment During Ascending and Descending Phases of Intoxication. J Stud Alcohol Drugs 2019; 80:236-244. [PMID: 31014469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023] Open
Abstract
OBJECTIVE Visuospatial awareness is critical for everyday activities like driving. Higher order processes, such as visuospatial working memory (VSWM) and top-down modulation of gaze control, enable goal-driven visual scanning. Although available evidence suggests that alcohol differentially affects VSWM during the ascending and descending phases of the blood alcohol concentration (BAC) curve, it remains unclear whether such impact extends to a systemic disruption of visual scanning behavior. METHOD In a placebo-controlled and repeated-measures design, the present study investigated the influence of moderate alcohol intake (0.6 g/kg) on VSWM and gaze behavior by using gaze entropy measures to quantify visual scanning efficiency. Thirty-eight (18 female, 20 male) healthy participants completed a VSWM task across three consecutive sessions (baseline, ascending, descending) while their eye movements were simultaneously recorded. RESULTS Performance in VSWM was affected during the descending session, where response accuracy declined significantly. Stationary gaze entropy (SGE) and gaze transition entropy (GTE) measures significantly reduced during both ascending and descending sessions. Fixation rate and duration were also affected by alcohol, but only during the ascending session. CONCLUSIONS Reduction in SGE suggests a less explorative distribution of gaze, whereas low GTE is indicative of reduced visual scanning efficiency. These findings reflect the detrimental effects of alcohol on top-down control of gaze behavior, which may limit visual scanning efficiency. Deficits in visual scanning efficiency across the blood alcohol concentration curve may reduce visuospatial awareness and contribute to unintentional injuries during periods of intoxication.
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Affiliation(s)
- Brook Shiferaw
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
| | - Luke A Downey
- Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn, Australia
- Institute for Breathing and Sleep, Austin Hospital, Melbourne, Australia
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Brown A, Corner M, Crewther D, Crewther S. Age Related Decline in Cortical Multifocal Flash VEP: Latency Increases Shown to Be Predominately Magnocellular. Front Aging Neurosci 2019; 10:430. [PMID: 30713495 PMCID: PMC6345711 DOI: 10.3389/fnagi.2018.00430] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Accepted: 12/14/2018] [Indexed: 12/18/2022] Open
Abstract
As the visual system ages, flicker sensitivity decreases and the latencies of cortical visual evoked potentials (VEP) increase. However, the extent to which these effects reflect age-related changes in the magnocellular (M) and or parvocellular (P) pathways remain unclear. Here, we investigated the relation between flicker fusion frequencies and VEP non-linearities induced by rapid stimulation, as a function of age over 6 decades. The approach, using Wiener kernel analysis of multifocal flash (mf)VEP, allows the extraction of signatures of both M and P processing and hence establishing a neural basis of the known decline in flicker fusion threshold. We predicted that, in a sample of 86 participants, age would be associated with a latency increase in early mfVEP response components and that flicker fusion thresholds, for both low and high contrast stimuli, would relate to the temporal efficiency of the M-generated VEP component amplitudes. As expected, flicker fusion frequency reduced with age, while latencies of early second order peaks of the mfVEP increased with age, but M temporal efficiency (amplitude ratio of first to second order peaks) was not strongly age-related. The steepest increases in latency were associated with the M dominated K2.1 (second order first slice) N70 components recorded at low and high contrast (6.7 and 5.9 ms/decade, respectively). Interestingly, significant age-related latency shifts were not observed in the first order responses. Significant decreases in amplitude were found in multiple first and second order components up to 30 years of age, after which they remained relatively constant. Thus, aging and decline in visual function appears to be most closely related to the response latencies of non-linearities generated by the M pathway.
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Affiliation(s)
- Alyse Brown
- School of Psychological Science and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - Molly Corner
- School of Psychological Science and Public Health, La Trobe University, Melbourne, VIC, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, VIC, Australia
| | - Sheila Crewther
- School of Psychological Science and Public Health, La Trobe University, Melbourne, VIC, Australia
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Wijeratne T, Tang H, Crewther D, Crewther S. Prevalence of Migraine in the Elderly: A Narrated Review. Neuroepidemiology 2019; 52:104-110. [DOI: 10.1159/000494758] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 10/21/2018] [Indexed: 11/19/2022] Open
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Shiferaw B, Downey L, Crewther D. A review of gaze entropy as a measure of visual scanning efficiency. Neurosci Biobehav Rev 2019; 96:353-366. [DOI: 10.1016/j.neubiorev.2018.12.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 12/05/2018] [Accepted: 12/06/2018] [Indexed: 11/16/2022]
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Hugrass L, Crewther D. The effects of figure-ground segmentation on non-linear visual evoked potentials. J Vis 2018. [DOI: 10.1167/18.10.333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Laila Hugrass
- Centre for Human Psychopharmacology, Swinburne University of Technology
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology
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Crewther S, Lamp G, Goodin P, Laycock R, Crewther D. Cerebellum added to Working Memory Networks revealed by Meta-analysis of Activation Likelihood Estimation of fMRI sites in n-back tasks. J Vis 2018. [DOI: 10.1167/18.10.688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Sheila Crewther
- School of Psychology and Public Health, La Trobe University, Melbourne, Victoria, Australia
| | - Gemma Lamp
- School of Psychology and Public Health, La Trobe University, Melbourne, Victoria, Australia
| | - Peter Goodin
- Florey Institute of Neuroscience and Mental Health, Heidelberg, Victoria, AustraliaCentre for Human Psychopharmacology, Swinburne University, Melbourne, Victoria, Australia
| | - Robin Laycock
- School of Psychology and Public Health, La Trobe University, Melbourne, Victoria, Australia.School of Health and Biomedical Sciences, RMIT University, Melbourne, Victoria, Australia
| | - David Crewther
- School of Psychology and Public Health, La Trobe University, Melbourne, Victoria, Australia.Centre for Human Psychopharmacology, Swinburne University, Melbourne, Victoria, Australia
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Crewther D, Hugrass L, Price A, Labuschagne I. Nasal Oxytocin produces emotion dependent effects on early visual evoked potentials. J Vis 2018. [DOI: 10.1167/18.10.911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology
| | - Laila Hugrass
- Centre for Human Psychopharmacology, Swinburne University of Technology
| | - Ariane Price
- Centre for Human Psychopharmacology, Swinburne University of Technology
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Burt A, Hugrass L, Frith-Belvedere T, Crewther D. Insensitivity to Fearful Emotion for Early ERP Components in High Autistic Tendency Is Associated with Lower Magnocellular Efficiency. Front Hum Neurosci 2017; 11:495. [PMID: 29075185 PMCID: PMC5643484 DOI: 10.3389/fnhum.2017.00495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/26/2017] [Indexed: 01/12/2023] Open
Abstract
Low spatial frequency (LSF) visual information is extracted rapidly from fearful faces, suggesting magnocellular involvement. Autistic phenotypes demonstrate altered magnocellular processing, which we propose contributes to a decreased P100 evoked response to LSF fearful faces. Here, we investigated whether rapid processing of fearful facial expressions differs for groups of neurotypical adults with low and high scores on the Autistic Spectrum Quotient (AQ). We created hybrid face stimuli with low and high spatial frequency filtered, fearful, and neutral expressions. Fearful faces produced higher amplitude P100 responses than neutral faces in the low AQ group, particularly when the hybrid face contained a LSF fearful expression. By contrast, there was no effect of fearful expression on P100 amplitude in the high AQ group. Consistent with evidence linking magnocellular differences with autistic personality traits, our non-linear VEP results showed that the high AQ group had higher amplitude K2.1 responses than the low AQ group, which is indicative of less efficient magnocellular recovery. Our results suggest that magnocellular LSF processing of a human face may be the initial visual cue used to rapidly and automatically detect fear, but that this cue functions atypically in those with high autistic tendency.
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Affiliation(s)
- Adelaide Burt
- Centre for Human Psychopharmacology, Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne, VIC, Australia
| | - Laila Hugrass
- Centre for Human Psychopharmacology, Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne, VIC, Australia
| | - Tash Frith-Belvedere
- Centre for Human Psychopharmacology, Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne, VIC, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne, VIC, Australia
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Brown A, Corner M, Crewther D, Crewther S. Human flicker fusion frequencies correlate negatively with cortical VEP magnocellular nonlinearities. J Vis 2017. [DOI: 10.1167/17.10.735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Alyse Brown
- School of Psychology and Public Health, La Trobe University
| | - Molly Corner
- School of Psychology and Public Health, La Trobe University
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology
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Hugrass L, Crewther D. The effects of visual surround on multifocal visual evoked potentials. J Vis 2017. [DOI: 10.1167/17.10.793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Laila Hugrass
- Centre for Human Psychopharmacology, Swinburne University of Technology
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology
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Crewther D, Ye R, Jian Y, Lai HY. Orientation surround suppression but not complex search slope correlates with autistic trait level. J Vis 2017. [DOI: 10.1167/17.10.702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- David Crewther
- ZIINT, Zhejiang UniversityCHP, Swinburne University of Technology
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Abstract
"The dress" has provoked intensive commentary among psychophysicists, especially in relation to color vision. Researchers have shown that manipulating illuminance cues can influence the perceived colors of the dress. Here we investigate whether illusory shifts in brightness can shift color perception of the dress. Drifting achromatic gratings with fast off and fast on shading profiles are known to give an illusion of brightening or darkening, respectively. We superimposed rotating sawtooth gratings on a series of dress images that morphed from extreme white/gold through to blue/black. In a sample of 18 adults (11 with white/gold dress percept and seven with blue/black percept), a two-alternative, forced-choice constant stimulus task measured the morphed image point at which each observer was equally likely to categorize the dress as white/gold or blue/black (the point of subjective equality or PSE). Despite manifest individual differences in the PSE, the two sawtooth temporal profiles consistently changed the perceived colors of the dress. Perceptual dimming shifted color categorization toward blue/black whereas perceptual brightening shifted color categorization toward white/gold. We conclude that color categorization is influenced substantially by illusory shifts in brightness.
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Affiliation(s)
- Laila Hugrass
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne,
| | - Jana Slavikova
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, Australia
| | - Melissa Horvat
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, Australia
| | - Alaa Al Musawi
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, Australia
| | - David Crewther
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne,
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Hugrass L, Burt A, Firth-Belvedere T, Crewther D. Does early processing of low-spatial frequency fearful facial expressions vary as a function of autistic tendency? J Vis 2016. [DOI: 10.1167/16.12.167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther D, Riddell N, Hugrass L, Jayasuriya J, Crewther S. Toad lights up the prince of brightness illusions. J Vis 2016. [DOI: 10.1167/16.12.561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Abstract
In the present study, direct evidence was sought linking cognitive automatic processing with reading in the general adult population. Reading speed on single-task performance and dual-task performance were compared. A total of 18 adults without dyslexia participated (7 men and 11 women, age M = 25.3 yr., SD = 2.7). Participants initially were trained in single-task mode on two types of tasks. The first was a central alphanumeric equation task (true or false), which comprised 3 subtests of increasing difficulty, ranging from an easily automated task to a varied and unpredictable mathematical operation. The second task was a peripheral pattern subitization task for which stimulus exposure time was related to performance. Finally, participants received dual-task training, which required simultaneous processing of both tasks. Slower reading speed was significantly related to rate of learning and speed of performance on predictable alphanumeric operations in dual-task conditions. There was no effect of reading speed on performance in the varied alphanumeric task. Faster readers were no better than slower readers on the pattern-subitization task. These findings suggest that faster readers automatized the predictable alphanumeric task more rapidly than slower readers and hence were better able to cope with the dual-task condition.
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Affiliation(s)
- Rozalia Hecht
- Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
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Thompson J, Crewther D. The attentional strobe: auditory manipulation of visual conscious awareness. J Vis 2015. [DOI: 10.1167/15.12.1251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther D. Temporal structure of Human Magnetic Evoked Fields to Colour, Form and Motion. J Vis 2014. [DOI: 10.1167/14.10.984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Bauer I, Hughes M, Rowsell R, Cockerell R, Pipingas A, Crewther S, Crewther D. Omega-3 supplementation improves cognition and modifies brain activation in young adults. Hum Psychopharmacol 2014; 29:133-44. [PMID: 24470182 DOI: 10.1002/hup.2379] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Revised: 09/26/2013] [Accepted: 11/11/2013] [Indexed: 01/21/2023]
Abstract
OBJECTIVE The current study aimed to investigate the effects of eicosapentaenoic acid (EPA)-rich and docosahexaenoic acid (DHA)-rich supplementations on cognitive performance and functional brain activation. DESIGN A double-blind, counterbalanced, crossover design, with a 30-day washout period between two supplementation periods (EPA-rich and DHA-rich) was employed. Functional magnetic resonance imaging scans were obtained during performance of Stroop and Spatial Working Memory tasks prior to supplementation and after each 30-day supplementation period. RESULTS Both supplementations resulted in reduced ratio of arachidonic acid to EPA levels. Following the EPA-rich supplementation, there was a reduction in functional activation in the left anterior cingulate cortex and an increase in activation in the right precentral gyrus coupled with a reduction in reaction times on the colour-word Stroop task. By contrast, the DHA-rich supplementation led to a significant increase in functional activation in the right precentral gyrus during the Stroop and Spatial Working Memory tasks, but there was no change in behavioural performance. CONCLUSIONS By extending the theory of neural efficiency to the within-subject neurocognitive effects of supplementation, we concluded that following the EPA-rich supplementation, participants' brains worked 'less hard' and achieved a better cognitive performance than prior to supplementation. Conversely, the increase in functional activation and lack of improvement in time or accuracy of cognitive performance following DHA-rich supplementation may indicate that DHA-rich supplementation is less effective than EPA-rich supplementation in enhancing neurocognitive functioning after a 30-day supplementation period in the same group of individuals.
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Affiliation(s)
- Isabelle Bauer
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Australia
| | - Matthew Hughes
- Brain and Psychological Sciences Research Centre; Swinburne University of Technology; Hawthorn Australia
| | - Renee Rowsell
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Australia
| | - Robyn Cockerell
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Australia
| | - Andrew Pipingas
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Australia
| | - Sheila Crewther
- School of Psychological Sciences; La Trobe University; Bundoora Australia
| | - David Crewther
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Australia
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Bauer I, Crewther S, Pipingas A, Sellick L, Crewther D. Does omega-3 fatty acid supplementation enhance neural efficiency? A review of the literature. Hum Psychopharmacol 2014; 29:8-18. [PMID: 24285504 DOI: 10.1002/hup.2370] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 10/19/2013] [Accepted: 10/20/2013] [Indexed: 11/08/2022]
Abstract
OBJECTIVE While the cardiovascular, anti-inflammatory and mood benefits of omega-3 supplementation containing long chain fatty acids (LCPUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are manifest, there is no scientific consensus regarding their effects on neurocognitive functioning. This review aimed to examine the current literature on LCPUFAs by assessing their effects on cognition, neural functioning and metabolic activity. In order to view these findings together, the principle of neural efficiency as established by Richard Haier ("smart brains work less hard") was extended to apply to the neurocognitive effects of omega-3 supplementation. METHODS We reviewed multiple databases from 2000 up till 2013 using a systematic approach and focused our search to papers employing both neurophysiological techniques and cognitive measures. RESULTS Eight studies satisfied the criteria for consideration. We established that studies using brain imaging techniques show consistent changes in neurochemical substances, brain electrical activity, cerebral metabolic activity and brain oxygenation following omega-3 supplementation. CONCLUSIONS We conclude that, where comparison is available, an increase in EPA intake is more advantageous than DHA in reducing "brain effort" relative to cognitive performance.
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Affiliation(s)
- Isabelle Bauer
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Victoria Australia
- University of Texas, Health Science Center at Houston; Department of Psychiatry and Behavioral Sciences; Houston TX USA
| | - Sheila Crewther
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Victoria Australia
- School of Psychological Science; La Trobe University; Bundoora Victoria Australia
| | - Andrew Pipingas
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Victoria Australia
| | - Laura Sellick
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Victoria Australia
| | - David Crewther
- Centre for Human Psychopharmacology; Swinburne University of Technology; Hawthorn Victoria Australia
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Crewther D, Brown A, Hugrass L. Spatio-temporal structure of multi-focal MEG potentials shows evidence of striate global/local signalling. J Vis 2013. [DOI: 10.1167/13.9.308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Vukusic S, Crewther D, Ciorciari J, Kaufman J. P2-27: Electrophysiological Correlates of Conscious and Unconscious Processing of Emotional Faces in Individuals with High and Low Autistic Traits. Iperception 2012. [DOI: 10.1068/if686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Hugrass L, Crewther D. The Relationship between Pursuit Eye Movements and Perception during Binocular Rivalry. Iperception 2012. [DOI: 10.1068/if743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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30
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Crewther D, Jackson B, Blackwood E, Blum J, Carruthers S, Nemorin S, Pryor B, Sceneay S, Bevan S, Slikboer R. Contrast response functions for visual evoked nonlinearities demonstrate differences in magnocellular but not parvocellular components as a function of autistic tendency. J Vis 2012. [DOI: 10.1167/12.9.1356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther S, Laycock R, Crewther D. Both abrupt and ramped onset of contrast reversing phantom contours reveals a magnocellular impairment in dyslexia. J Vis 2012. [DOI: 10.1167/12.9.527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Laycock R, Alexander B, Crewther D, Crewther S. Critical timing of dorsal and ventral visual streams in abrupt and ramped onset object recognition. J Vis 2012. [DOI: 10.1167/12.9.521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Murphy M, Laycock R, Goharpey N, Bridie J, Faragalla D, Fithall K, Hodge K, Hodgson A, Hoystead C, Koyu Z, Shilton A, Tsoutsoulis K, Ucarli C, Brown A, Crewther D, Crewther S. The Role of Dorsal Stream Development in Form and Motion Coherence and Object Recognition: The Childhood Challenge of Processing Transient Events. J Vis 2012. [DOI: 10.1167/12.9.1368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther D, Crewther D, Crewther S. The effects of saccades on magnocellular visual function in high and low autistic tendency. J Vis 2011. [DOI: 10.1167/11.11.437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther D, Sutherland A. Magnocellular VEP delay in high Autism Quotient individuals: Absence of the magnocellular advantage may explain poor global identification of locally salient Navon figures. J Vis 2010. [DOI: 10.1167/9.8.87] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Crewther D, Crewther D, Ashton M, Kuang A. Left global visual hemineglect in high Autism-spectrum Quotient (AQ) individuals. J Vis 2010. [DOI: 10.1167/10.7.358] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Hugrass L, Crewther D, Alais D. The effects of motion on binocular rivalry between simple and complex images. J Vis 2010. [DOI: 10.1167/8.6.801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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39
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Crewther S, Laycock R, Fitzgerald P, Crewther D. Evidence for an early, direct visual input to V5/MT. J Vis 2010. [DOI: 10.1167/6.6.571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Jackson ML, Croft RJ, Owens K, Pierce RJ, Kennedy GA, Crewther D, Howard ME. The effect of acute sleep deprivation on visual evoked potentials in professional drivers. Sleep 2008; 31:1261-1269. [PMID: 18788651 PMCID: PMC2542966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023] Open
Abstract
STUDY OBJECTIVES Previous studies have demonstrated that as little as 18 hours of sleep deprivation can cause deleterious effects on performance. It has also been suggested that sleep deprivation can cause a "tunnel-vision" effect, in which attention is restricted to the center of the visual field. The current study aimed to replicate these behavioral effects and to examine the electrophysiological underpinnings of these changes. DESIGN Repeated-measures experimental study. SETTING University laboratory. PATIENTS OR PARTICIPANTS Nineteen professional drivers (1 woman; mean age = 45.3 +/- 9.1 years). INTERVENTIONS Two experimental sessions were performed; one following 27 hours of sleep deprivation and the other following a normal night of sleep, with control for circadian effects. MEASUREMENTS & RESULTS A tunnel-vision task (central versus peripheral visual discrimination) and a standard checkerboard-viewing task were performed while 32-channel EEG was recorded. For the tunnel-vision task, sleep deprivation resulted in an overall slowing of reaction times and increased errors of omission for both peripheral and foveal stimuli (P < 0.05). These changes were related to reduced P300 amplitude (indexing cognitive processing) but not measures of early visual processing. No evidence was found for an interaction effect between sleep deprivation and visual-field position, either in terms of behavior or electrophysiological responses. Slower processing of the sustained parvocellular visual pathway was demonstrated. CONCLUSIONS These findings suggest that performance deficits on visual tasks during sleep deprivation are due to higher cognitive processes rather than early visual processing. Sleep deprivation may differentially impair processing of more-detailed visual information. Features of the study design (eg, visual angle, duration of sleep deprivation) may influence whether peripheral visual-field neglect occurs.
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Affiliation(s)
- Melinda L Jackson
- Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia.
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Thompson JC, Hardee JE, Panayiotou A, Crewther D, Puce A. Common and distinct brain activation to viewing dynamic sequences of face and hand movements. Neuroimage 2007; 37:966-73. [PMID: 17616403 DOI: 10.1016/j.neuroimage.2007.05.058] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 04/17/2007] [Accepted: 05/23/2007] [Indexed: 11/22/2022] Open
Abstract
The superior temporal sulcus (STS) and surrounding lateral temporal and inferior parietal cortices are an important part of a network involved in the processing of biological movement. It is unclear whether the STS responds to the movement of different body parts uniformly, or if the response depends on the body part that is moving. Here we examined brain activity to recognizing sequences of face and hand movements as well as radial grating motion, controlling for differences in movement dynamics between stimuli. A region of the right posterior STS (pSTS) showed common activation to both face and hand motion, relative to radial grating motion, with no significant difference between responses to face and hand motion in this region. Distinct responses to face motion relative to hand motion were observed in the right mid-STS, while the right posterior inferior temporal sulcus (pITS) and inferior parietal lobule (IPL) showed greater responses to hand motion relative to face motion. These findings indicate that while there may be distinct processing of different body part motion in lateral temporal and inferior parietal cortices, the response of the pSTS is not body part specific. This region may provide input to other parts of a network involved with processing human actions with a high-level visual description of biological motion.
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Affiliation(s)
- James C Thompson
- Department of Psychology and Krasnow Institute for Advanced Study, George Mason University, MSN 3F5, Fairfax, VA 22030, USA.
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Keage HAD, Clark CR, Hermens DF, Kohn MR, Clarke S, Williams LM, Crewther D, Lamb C, Gordon E. DISTRACTIBILITY IN AD/HD PREDOMINANTLY INATTENTIVE AND COMBINED SUBTYPES: THE P3a ERP COMPONENT, HEART RATE AND PERFORMANCE. J Integr Neurosci 2006; 5:139-58. [PMID: 16544371 DOI: 10.1142/s0219635206001070] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 02/08/2006] [Indexed: 11/18/2022] Open
Abstract
The current study aimed to investigate whether children and adolescents diagnosed with Attention Deficit/Hyperactivity Disorder Predominantly Inattentive (AD/HD-in; Child n = 24, Adolescent n = 33) and Combined (AD/HD-com; Child n = 30, Adolescent n = 42) subtypes were more distractible than controls (Child n = 54; Adolescents n = 75), by assessing event-related potential (ERP), performance and peripheral arousal measures. All AD/HD groups displayed smaller amplitudes and/or shorter latencies of the P3a ERP component - thought to reflect involuntary attention switching - following task-deviant novel stimuli (checkerboard patterns) embedded in a Working Memory (WM) task. The P3a results suggested that both AD/HD-in and AD/HD-com subtypes ineffectively evaluate deviant stimuli and are hence more "distractible". These abnormalities were most pronounced over the central areas. AD/HD groups did not display any abnormalities in averaged heart rate over the WM task, a measure of peripheral arousal. They did display abnormalities in performance measures from the task, but these were unrelated to P3a abnormalities. AD/HD groups also displayed a number of deficits on Switching of Attention and Verbal Memory tasks, however, the pattern of abnormality mostly reflected general cognitive deficits rather than resulting from distraction.
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Affiliation(s)
- Hannah A D Keage
- Cognitive Neuroscience Laboratory, School of Psychology, Flinders University, SA 5042, Australia
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Abstract
A 35-year-old woman who reported persistent significant vision loss for 3 years after taking the antidepressant nefazodone was referred for electrophysiological assessment of vision. The vision changes included reduced acuities, reduced colour vision and visual field constriction in both eyes and were thought to be associated with the use of nefazodone for 6 - 8 weeks, 3 years earlier. Multifocal electroretinograms and visual evoked potentials were recorded using the Visual Evoked Response Imaging System (VERIS) to investigate the nature and site of the neural deficit. The summed retinal response showed a normal a- and b-wave latency and amplitude, however, the retinal topographic mfERGs showed a severe depression of the macular response in both eyes. The cortical topographic multifocal VEP mapping also showed a central depression in the right eye compared with the left. Two-frame motion and pattern custom mfVEP were also measured to assess different forms of cortical processing and especially of motion as nefazodone has previously been associated with image persistence with moving stimuli. The responses to two frame-motion showed signs of abnormality. Thus these results suggest that the primary locus of neural damage is retinal and is likely to have resulted from neurotoxicity. Other competing hypotheses such as hysterical blindness must be ruled out.
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Affiliation(s)
- Chi Luu
- School of Psychological Science, La Trobe University, Bundoora, VIC 3086, Australia
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Abstract
This is the second of a two-part survey of current literature concerning strabismic amblyopia. The aim of this review is to bring the optometric community up to date on the status of scientific research into strabismic amblyopia. Part 1 in this series discussed research into strabismic amblyopia from the viewpoint of psychophysical experiments, which investigate both spatial and temporal behavioural deficits accompanying strabismic amblyopia. These include deficits in contrast sensitivity, spatial localisation, fixation, ocular motility, accommodation, crowding, attention, motion perception and temporal processing. Part 2 concerns neural processing in regards to strabismic amblyopia. It discusses current understanding of more fundamental aspects of central processing of visual information and in particular current theories regarding neural sites and mechanisms involved in amblyopia.
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Affiliation(s)
- Lisa Asper
- School of Optometry, The University of New South Wales, Sydney, New South Wales, 2052, Australia
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Abstract
This is a two-part survey of current literature concerning strabismic amblyopia. The aim of this review is to bring the optometric practitioner up to date on the status of scientific research into strabismic amblyopia. Part 1 in this series discusses research into strabismic amblyopia from the viewpoint of psychophysical experiments that investigate both spatial and temporal behavioural deficits accompanying strabismic amblyopia. These include deficits in contrast sensitivity, spatial localisation, fixation, ocular motility, accommodation, crowding, attention, motion perception and temporal processing. Part 2 will evaluate neural processing in regard to strabismic amblyopia. It will discuss current understanding of aspects of central processing of visual information and theories regarding neural sites and mechanisms involved in amblyopia.
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Affiliation(s)
- Lisa Asper
- School of Optometry, The University of New South Wales, Sydney, New South Wales, 2052, Australia
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Junghans B, Crewther S, Crewther D. Fine structure of lymphatics in the avian choroid. Invest Ophthalmol Vis Sci 1998; 39:854-5. [PMID: 9538897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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Abstract
Tone bursts produced bands of selective 2-[14C]-deoxyglucose labelling in the inferior colliculus (IC) of the awake monkey. Low tone frequencies produced labelling in dorsal regions and high tone frequencies produced labelling in ventral regions. The position of the bands coincided with the position of a single unit with a characteristic frequency, which was the same as the frequency producing the labelling. These findings indicate that the bands of labelling represent iso-frequency contours in IC. The iso-frequency contours extended across most of the nucleus and were oriented from dorsomedially to ventro-laterally at 20-30 degrees from the horizontal and became more vertical anteriorly. The width of the contours was as narrow as 200 micron, suggesting that the contours might represent 2 or 3 overlapping cellular laminae.
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