High-dose Vitamin B6 supplementation reduces anxiety and strengthens visual surround suppression

OBJECTIVE

Vitamins B6 and B12 are involved in metabolic processes that decrease neural excitation and increase inhibition. This double-blind study investigated the effects of supplementation for 1 month with a high-dose of B6 or B12, compared to placebo, on a range of behavioural outcome measures connected to the balance between neural inhibition and excitation.

METHODS

478 young adults were recruited over five linked phases. Self-reported anxiety (N = 265) and depression (N = 146) were assessed at baseline and after supplementation. Several sensory measures acted as assays of inhibitory function and were assessed post-supplementation only; these were surround suppression of visual contrast detection (N = 307), binocular rivalry reversal rate (N = 172), and a battery of tactile sensitivity tests (N = 180).

RESULTS

Vitamin B6 supplementation reduced self-reported anxiety and induced a trend towards reduced depression, as well as increased surround suppression of visual contrast detection, but did not reliably influence the other outcome measures. Vitamin B12 supplementation produced trends towards changes in anxiety and visual processing.

CONCLUSIONS

Our results suggest that high-dose Vitamin B6 supplementation increases inhibitory GABAergic neural influences, which is consistent with its known role in the synthesis of GABA.

rTMS of the superior parietal lobule improves contrast discrimination but has no effect on the perception of distance between stimuli in the image plane

The superior parietal lobule (SPL) is a region of the brain that has been associated with a diverse range of high-level visual and cognitive functions. This suggested the possibility that it supports a lower-level function that is engaged by a wide range of experimental tasks. Analysis of tasks used in previous studies suggests that one such lower-level function might be the perception of the distance between stimuli in the image plane. In this study, we applied online high-frequency repetitive transcranial magnetic stimulation (rTMS) over the left SPL or the vertex in order to further investigate the role played by this region in the perceived visual separation between points. As a control task, we asked participants to detect the difference in contrast between two Gabor patches. The results failed to support the main hypothesis, but we unexpectedly found that rTMS to left SPL improved peripheral contrast discrimination. Previous studies have found that rTMS to the right frontal eye field, which has strong functional connectivity with the SPL, has the same effect, suggesting the two areas work together to influence early visual areas.

Supplemental Vitamin B-12 Enhances the Neural Response to Sensory Stimulation in the Barrel Cortex of Healthy Rats but Does Not Affect Spontaneous Neural Activity

BACKGROUND

Although vitamin B-12 (B-12) is known to contribute to the structural and functional development of the brain, it is unclear if B-12 supplementation has any beneficial effect in healthy populations in terms of enhanced neurologic status of the brain or improved cognitive function.

OBJECTIVES

We investigated the effect of dietary supplementation of B-12 on the cortical neural activity of well-nourished young adult rats and tested the hypothesis that B-12 supplementation in healthy rats may reduce sensory-evoked neural activity due to enhanced inhibition.

METHODS

Female Lister Hooded rats weighing 190-265 g (2-4 mo old) were included in the study. The experimental group was fed with B-12 (cyanocobalamin)-enriched water at a concentration of 1 mg/L, and the control (CON) group with tap water for 3 wk. Animals were then anesthetized and cortical neural responses to whisker stimulation were recorded in vivo through the use of a multichannel microelectrode, from which local field potentials (LFPs) were extracted.

RESULTS

Somatosensory-evoked LFP was 25% larger in the B-12 group (4.13 ± 0.24 mV) than in the CON group (3.30 ± 0.21 mV) (P = 0.02). Spontaneous neural activity did not differ between groups; frequency spectra at each frequency bin of interest did not pass the cluster-forming threshold at the 5% significance level.

CONCLUSIONS

These findings do not provide evidence supporting the hypothesis of decreased neural activity due to B-12 supplementation. As the spontaneous neural activity was unaffected, the increase in somatosensory-evoked LFP may be due to enhanced afferent signal reaching the barrel cortex from the whisker pad, indicating that B-12-supplemented rats may have enhanced sensitivity to sensory stimulation compared with the CON group. We suggest that this enhancement might be the result of lowered sensory threshold, although the underlying mechanism has yet to be elucidated.

Practice effects in nutrition intervention studies with repeated cognitive testing

BACKGROUND:

There is growing interest in the use of nutrition interventions to improve cognitive function. To determine intervention efficacy, repeated cognitive testing is often required. However, performance on tasks can improve through practice, irrespective of any intervention.

OBJECTIVE:

This study investigated practice effects for commonly used cognitive tasks (immediate and delayed recall, serial subtractions, Stroop and the Sternberg task) to identify appropriate methodology for minimising their impact on nutrition intervention outcomes.

METHODS:

Twenty-nine healthy young adults completed six repetitions of the cognitive battery (two sessions on each of three separate visits). Subjective measures of mood, motivation and task difficulty were also recorded at each repetition.

RESULTS:

Significant practice effects were apparent for all tasks investigated and were attenuated, but not fully eliminated, at later visits compared with the earlier visits. Motivation predicted cognitive performance for the tasks rated most difficult by participants (serial 7s, immediate and delayed recall). While increases in mental fatigue and corresponding decreases in positive mood were observed between test sessions occurring on the same day, there were no negative consequences of long term testing on mood across the duration of the study.

CONCLUSION:

Practice effects were evident for all investigated cognitive tasks, with strongest effects apparent between visits one and two. Methodological recommendations to reduce the impact of practice on the statistical power of future intervention studies have been made, including the use of alternate task forms at each repetition and the provision of a familiarisation visit on a separate day prior to data collection.

Visual processing of optic flow and motor control in the human posterior cingulate sulcus

Previous studies have shown that the human posterior cingulate contains a visual processing area selective for optic flow (CSv). However, other studies performed in both humans and monkeys have identified a somatotopic motor region at the same location (CMA). Taken together, these findings suggested the possibility that the posterior cingulate contains a single visuomotor integration region. To test this idea we used fMRI to identify both visual and motor areas of the posterior cingulate in the same brains and to test the activity of those regions during a visuomotor task. Results indicated that rather than a single visuomotor region the posterior cingulate contains adjacent but separate motor and visual regions. CSv lies in the fundus of the cingulate sulcus, while CMA lies in the dorsal bank of the sulcus, slightly superior in terms of stereotaxic coordinates. A surprising and novel finding was that activity in CSv was suppressed during the visuomotor task, despite the visual stimulus being identical to that used to localize the region. This may provide an important clue to the specific role played by this region in the utilization of optic flow to control self-motion.

The neural basis of centre-surround interactions in visual motion processing

Perception of a moving visual stimulus can be suppressed or enhanced by surrounding context in adjacent parts of the visual field. We studied the neural processes underlying such contextual modulation with fMRI. We selected motion selective regions of interest (ROI) in the occipital and parietal lobes with sufficiently well defined topography to preclude direct activation by the surround. BOLD signal in the ROIs was suppressed when surround motion direction matched central stimulus direction, and increased when it was opposite. With the exception of hMT+/V5, inserting a gap between the stimulus and the surround abolished surround modulation. This dissociation between hMT+/V5 and other motion selective regions prompted us to ask whether motion perception is closely linked to processing in hMT+/V5, or reflects the net activity across all motion selective cortex. The motion aftereffect (MAE) provided a measure of motion perception, and the same stimulus configurations that were used in the fMRI experiments served as adapters. Using a linear model, we found that the MAE was predicted more accurately by the BOLD signal in hMT+/V5 than it was by the BOLD signal in other motion selective regions. However, a substantial improvement in prediction accuracy could be achieved by using the net activity across all motion selective cortex as a predictor, suggesting the overall conclusion that visual motion perception depends upon the integration of activity across different areas of visual cortex.

Consumption of cocoa flavanols results in an acute improvement in visual and cognitive functions

Cocoa flavanols (CF) influence physiological processes in ways that suggest their consumption may improve aspects of neural function, and previous studies have found positive influences of CF on cognitive performance. In this preliminary study we investigated whether visual, as well as cognitive, function is influenced by an acute dose of CF in young adults. We employed a randomized, single-blinded, order counterbalanced, crossover design in which 30 healthy adults consumed both dark chocolate containing 720mg CF and a matched quantity of white chocolate, with a one week interval between testing sessions. Visual contrast sensitivity was assessed by reading numbers that became progressively more similar in luminance to their background. Motion sensitivity was assessed firstly by measuring the threshold proportion of coherently moving signal dots that could be detected against a background of random motion, and secondly by determining the minimum time required to detect motion direction in a display containing a high proportion of coherent motion. Cognitive performance was assessed using a visual spatial working memory for location task and a choice reaction time task designed to engage processes of sustained attention and inhibition. Relative to the control condition, CF improved visual contrast sensitivity and reduced the time required to detect motion direction, but had no statistically reliable effect on the minimum proportion of coherent motion that could be detected. In terms of cognitive performance, CF improved spatial memory and performance on some aspects of the choice reaction time task. As well as extending the range of cognitive tasks that are known to be influenced by CF consumption, this is the first report of acute effects of CF on the efficiency of visual function. These acute effects can be explained by increased cerebral blood flow caused by CF, although in the case of contrast sensitivity there may be an additional contribution from CF induced retinal blood flow changes.

Neural processing of imminent collision in humans

Detecting a looming object and its imminent collision is imperative to survival. For most humans, it is a fundamental aspect of daily activities such as driving, road crossing and participating in sport, yet little is known about how the brain both detects and responds to such stimuli. Here we use functional magnetic resonance imaging to assess neural response to looming stimuli in comparison with receding stimuli and motion-controlled static stimuli. We demonstrate for the first time that, in the human, the superior colliculus and the pulvinar nucleus of the thalamus respond to looming in addition to cortical regions associated with motor preparation. We also implicate the anterior insula in making timing computations for collision events.

Interceptive timing: prior knowledge matters

Fast interceptive actions, such as catching a ball, rely upon accurate and precise information from vision. Recent models rely on flexible combinations of visual angle and its rate of expansion of which the tau parameter is a specific case. When an object approaches an observer, however, its trajectory may introduce bias into tau-like parameters that render these computations unacceptable as the sole source of information for actions. Here we show that observer knowledge of object size influences their action timing, and known size combined with image expansion simplifies the computations required to make interceptive actions and provides a route for experience to influence interceptive action.

Neural systems in the visual control of steering

Visual control of locomotion is essential for most mammals and requires coordination between perceptual processes and action systems. Previous research on the neural systems engaged by self-motion has focused on heading perception, which is only one perceptual subcomponent. For effective steering, it is necessary to perceive an appropriate future path and then bring about the required change to heading. Using function magnetic resonance imaging in humans, we reveal a role for the parietal eye fields (PEFs) in directing spatially selective processes relating to future path information. A parietal area close to PEFs appears to be specialized for processing the future path information itself. Furthermore, a separate parietal area responds to visual position error signals, which occur when steering adjustments are imprecise. A network of three areas, the cerebellum, the supplementary eye fields, and dorsal premotor cortex, was found to be involved in generating appropriate motor responses for steering adjustments. This may reflect the demands of integrating visual inputs with the output response for the control device.

The perception of emotion from body movement in point-light displays of interpersonal dialogue

We examined whether it is possible to identify the emotional content of behaviour from point-light displays where pairs of actors are engaged in interpersonal communication. These actors displayed a series of emotions, which included sadness, anger, joy, disgust, fear, and romantic love. In experiment 1, subjects viewed brief clips of these point-light displays presented the right way up and upside down. In experiment 2, the importance of the interaction between the two figures in the recognition of emotion was examined. Subjects were shown upright versions of (i) the original pairs (dyads), (ii) a single actor (monad), and (iii) a dyad comprising a single actor and his/her mirror image (reflected dyad). In each experiment, the subjects rated the emotional content of the displays by moving a slider along a horizontal scale. All of the emotions received a rating for every clip. In experiment 1, when the displays were upright, the correct emotions were identified in each case except disgust; but, when the displays were inverted, performance was significantly diminished for some emotions. In experiment 2, the recognition of love and joy was impaired by the absence of the acting partner, and the recognition of sadness, joy, and fear was impaired in the non-veridical (mirror image) displays. These findings both support and extend previous research by showing that biological motion is sufficient for the perception of emotion, although inversion affects performance. Moreover, emotion perception from biological motion can be affected by the veridical or non-veridical social context within the displays.

Perceiving time to collision activates the sensorimotor cortex

The survival of many animals hinges upon their ability to avoid collisions with other animals or objects, or to precisely control the timing of collisions. Optical expansion provides a compelling impression of object approach and in principle can provide the basis for judgments of time to collision (TTC) [1]. It has been demonstrated that pigeons [2] and houseflies [3] have neural systems that can initiate rapid coordinated actions on the basis of optical expansion. In the case of humans, the linkage between judgments of TTC and coordinated action has not been established at a cortical level. Using functional magnetic resonance imaging (fMRI), we identified superior-parietal and motor-cortex areas that are selectively active during perceptual TTC judgments, some of which are normally involved in producing reach-to-grasp responses. These activations could not be attributed to actual movement of participants. We demonstrate that networks involved in the computational problem of extracting TTC from expansion information have close correspondence with the sensorimotor systems that would be involved in preparing a timed motor response, such as catching a ball or avoiding collision.

Perceiving time to collision activates the sensorimotor cortex

The survival of many animals hinges upon their ability to avoid collisions with other animals or objects, or to precisely control the timing of collisions. Optical expansion provides a compelling impression of object approach and in principle can provide the basis for judgments of time to collision (TTC) [1]. It has been demonstrated that pigeons [2] and houseflies [3] have neural systems that can initiate rapid coordinated actions on the basis of optical expansion. In the case of humans, the linkage between judgments of TTC and coordinated action has not been established at a cortical level. Using functional magnetic resonance imaging (fMRI), we identified superior-parietal and motor-cortex areas that are selectively active during perceptual TTC judgments, some of which are normally involved in producing reach-to-grasp responses. These activations could not be attributed to actual movement of participants. We demonstrate that networks involved in the computational problem of extracting TTC from expansion information have close correspondence with the sensorimotor systems that would be involved in preparing a timed motor response, such as catching a ball or avoiding collision.

Temporal interval production and short-term memory

Interference with time estimation from concurrent nontemporal processing has been shown to depend on the short-term memory requirements of the concurrent task (Fortin & Breton, 1995; Fortin, Rousseau, Bourque, & Kirouac, 1993). In particular, it has been claimed that active processing of information in short-term memory produces interference, whereas simply maintaining information does not. Here, four experiments are reported in which subjects were trained to produce a 2,500-msec interval and then perform concurrent memory tasks. Interference with timing was demonstrated for concurrent memory tasks involving only maintenance. In one experiment, increasing set size in a pitch memory task systematically lengthened temporal production. Two further experiments suggested that this was due to a specific interaction between the short-term memory requirements of the pitch task and those of temporal production. In the final experiment, subjects performed temporal production while concurrently remembering the durations of a set of tones. Interference with interval production was comparable to that produced by the pitch memory task. Results are discussed in terms of a pacemaker-counter model of temporal processing, in which the counter component is supported by short-term memory.

Perceived relationships with parents among adolescent inpatients with depressive preoccupations and depressed mood

Hypothesized that two types of "depressogenic" preoccupations (self-critical and interpersonal), measured by the Depressive Experiences Questionnaire for adolescents (DEQ-A; Blatt, Shaffer, Bars, & Quinlan, 1992), would mediate associations between perceived difficulties with parents and adolescent depression. Adolescent inpatients between 11 and 17 years of age (N = 295; 158 girls) in an acute-care psychiatric hospital completed the DEQ-A, a Reynolds (1986, 1989) depression questionnaire, and measures that assess experiences of alienation (vs. dependency) and separation-individuation conflicts in the adolescent-parent relationship. Alienation and counterdependency in relation to parents were associated with self-critical concerns; excessive closeness and dependency with interpersonal concerns; and separation-individuation conflicts with both types of concerns. Self-critical and interpersonal concerns were linked to adolescent depression and accounted for most of the variance initially explained by difficulties with parents.