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Ross RG, Harris JG, Olincy A, Radant A. Eye movement task measures inhibition and spatial working memory in adults with schizophrenia, ADHD, and a normal comparison group. Psychiatry Res 2000; 95:35-42. [PMID: 10904121 DOI: 10.1016/s0165-1781(00)00153-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Schizophrenia and attention deficit/hyperactivity disorder (ADHD) are both associated with deficits in inhibition and working memory, although in ADHD the working memory deficit is hypothesized to be secondary to the inhibitory deficit. This similarity in cognitive processes has been paralleled by similarities across the two groups in the performance of working memory and inhibition tasks. The delayed oculomotor response task is an alternative task, which may allow greater separation of working memory from inhibitory components, and thus its use may provide additional information on primary vs. secondary deficits in these disorders. Ten young adult ADHD sufferers, 10 schizophrenic subjects, and 10 normal subjects were matched on age, gender, and education. Eye movements were recorded during delayed oculomotor response tasks with 1- and 3-s delays. Both the ADHD and the schizophrenic subjects demonstrated dis-inhibition (an increased percentage of premature saccades); however only schizophrenic subjects demonstrated an impaired working memory (decreased spatial accuracy of the remembered saccade). The results are consistent with the hypothesis that working memory is a primary deficit in schizophrenia, but secondary to the inhibitory deficit in ADHD.
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Olincy A, Ross RG, Harris JG, Young DA, McAndrews MA, Cawthra E, McRae KA, Sullivan B, Adler LE, Freedman R. The P50 auditory event-evoked potential in adult attention-deficit disorder: comparison with schizophrenia. Biol Psychiatry 2000; 47:969-77. [PMID: 10838065 DOI: 10.1016/s0006-3223(00)00239-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Attention-deficit/hyperactivity disorder (ADHD) and schizophrenia are both conceptualized as disorders of attention. Failure to inhibit the P50 auditory event-evoked response, extensively studied in schizophrenia, could also occur in ADHD patients, if these two illnesses have common underlying neurobiological substrates. METHODS This study examined the inhibition of the P50 auditory event-evoked potential in 16 unmedicated adults with ADHD, 16 schizophrenic outpatients, and 16 normal control subjects. Auditory stimuli were presented in a paired stimulus, conditioning-testing paradigm. RESULTS The amplitude of initial or conditioning P50 response did not differ between the three groups; however, significant effects of psychiatric diagnosis on the amplitude of the test response and the ratio of the test to the conditioning response amplitudes were observed. Schizophrenic patients' P50 ratios and test amplitudes were higher than both the ADHD and normal groups. CONCLUSIONS Adults with ADHD do not have the inhibitory deficit seen in patients with schizophrenia, suggesting that the mechanism of attentional disturbance in the two illnesses may be fundamentally different.
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Waldo MC, Adler LE, Leonard S, Olincy A, Ross RG, Harris JG, Freedman R. Familial transmission of risk factors in the first-degree relatives of schizophrenic people. Biol Psychiatry 2000; 47:231-9. [PMID: 10682220 DOI: 10.1016/s0006-3223(99)00272-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Schizophrenia is a complex illness with multiple pathophysiologic factors that contribute to its psychopathology. One strategy to identify these factors is to observe them in isolation from each other, by characterizing their expression in the relatives of schizophrenic probands. By Mendel's second law, each genetic factor should be independently distributed in a sibship, so that each can be observed by itself, uncomplicated by the general problems of the illness. Such independently distributed phenotypes are obviously useful for genetic analyses; however, they can also be considered together, to model how various brain dysfunctions may combine to produce psychoses. In addition to a sensory gating deficit linked to the alpha 7-nicotinic acetylcholine receptor locus, schizophrenics and their families have a number of other deficits, including decreased hippocampal volume on magnetic resonance images and increased plasma levels of the dopamine metabolite homovanillic acid. Although such research is far from complete, a heuristic model combining a sensory gating deficit, decreased hippocampal neuron capacity, and increased dopaminergic neurotransmission is consonant with current understanding of the neuropsychology of schizophrenia.
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Ross RG, Olincy A, Harris JG, Radant A, Adler LE, Compagnon N, Freedman R. The effects of age on a smooth pursuit tracking task in adults with schizophrenia and normal subjects. Biol Psychiatry 1999; 46:383-91. [PMID: 10435204 DOI: 10.1016/s0006-3223(98)00369-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Performance during a smooth pursuit eye movement (SPEM) task has been proposed as a marker of genetic risk for schizophrenia, although the precise component of SPEM tracking most associated with genetic risk remains undetermined. Normal adult aging is associated with deterioration on SPEM tasks; it remains unclear whether investigations of SPEM abnormalities will allow inclusion of older subjects in genetic studies. This study examines 1) the effect of normal aging on several components of SPEM performance; and 2) whether schizophrenic-normal differences found in young adults continue over a broad adult age span. METHODS SPEM was recorded during a 16.7 degrees per sec constant velocity task in 64 normal adults, ages 18 to 79 years, and 58 schizophrenic subjects, ages 18 to 70 years. RESULTS Smooth pursuit gain, the percent of total eye movements due to catch-up saccades, the frequency of large anticipatory saccades, and the frequency of leading saccades all deteriorate with increasing age. After correction for age, schizophrenic to control differences persist on most eye movement variables with the largest effect sizes for leading saccades (1.56) and smooth pursuit gain (1.17). CONCLUSIONS The tendency to use saccades to anticipate target motion, even in small steps (leading saccades), deserves further attention as a potential marker useful in genetic analyses.
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Ross RG, Olincy A, Radant A. Amplitude criteria and anticipatory saccades during smooth pursuit eye movements in schizophrenia. Psychophysiology 1999; 36:464-8. [PMID: 10432795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Increased frequency of anticipatory saccades during smooth pursuit eye movements is a potential marker of genetic risk for schizophrenia even in the absence of clinical symptomology. The operational definition of anticipatory saccades has often included an amplitude criterion; however, these amplitude criteria have often differed across studies. This study reports on the effect of varying amplitude criteria on the effect size in a comparison of 29 schizophrenic adults and 29 normal subjects during a 16.7 degrees/s constant velocity task. The inclusion of small amplitude anticipatory saccades, with amplitudes of 1-4 degrees, consistently increased effect size (largest effect size = 1.61). The inclusion of large anticipatory saccades, with amplitudes of 4 degrees or greater, had an inconsistent impact on effect size. The separation of anticipatory saccades into leading saccades (anticipatory saccades with amplitude 1-4 degrees) and large anticipatory saccades (amplitude > 4 degrees) deserves further exploration.
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Adler LE, Freedman R, Ross RG, Olincy A, Waldo MC. Elementary phenotypes in the neurobiological and genetic study of schizophrenia. Biol Psychiatry 1999; 46:8-18. [PMID: 10394470 DOI: 10.1016/s0006-3223(99)00085-2] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This review describes the strategy of using elementary phenotypes for neurobiological and genetic linkage studies of schizophrenia. The review concentrates on practical aspects of selecting the phenotype and then understanding the confounds in its measurement and interpretation. Examples from the authors' studies of deficits in P50 inhibition and smooth pursuit eye movement dysfunction are presented. These two phenotypes share considerable similarity in their neurobiology, including a similar response to nicotine. They also appear to co-segregate with the genetic risk for schizophrenia as autosomal co-dominant phenotypes. Although most schizophrenic patients inherit these abnormalities unilinealy, i.e., from one parent, apparent bilineal inheritance produces a more severe illness, observed clinically as childhood-onset schizophrenia. The initial study showing linkage of the P50 deficit to the chromosome 15q14 locus of the alpha 7-nicotinic acetylcholine receptor is an example of the potential usefulness of these phenotypes for combined genetic and neurobiological study of schizophrenia.
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Ross RG, Olincy A, Harris JG, Radant A, Hawkins M, Adler LE, Freedman R. Evidence for bilineal inheritance of physiological indicators of risk in childhood-onset schizophrenia. AMERICAN JOURNAL OF MEDICAL GENETICS 1999; 88:188-99. [PMID: 10206241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Childhood-onset schizophrenia is proposed to be associated with increased genetic loading compared with adult-onset schizophrenia because of its earlier age of onset and generally greater severity of symptoms. Diminished suppression of P50 auditory evoked responses to repeated stimuli and elevated anticipatory saccades during smooth pursuit eye movements are markers of genetic risk that are found in members of families with schizophrenia even in the absence of the full clinical disorder and appear to be transmitted in a single gene autosomal dominant fashion. Adult-onset schizophrenia is generally associated with one parent who demonstrates abnormal P50 sensory gating and elevated anticipatory saccades and one parent who is normal on the physiologic measures (i.e., unilineal inheritance). This study investigates whether childhood-onset schizophrenia is similarly unilineal or is associated with the inheritance of genetic risk factors from both parents (i.e., bilineal inheritance). Ten childhood-onset schizophrenic probands and their parents were studied. Their P50 sensory gating and anticipatory saccades were compared with adult-onset schizophrenic probands and their parents. Bilineality, measured as physiological impairment in both parents, occurred more frequently in childhood-onset probands than in adult-onset probands for both P50 sensory gating deficits (60% versus 13%) and elevated anticipatory saccades (60 versus 0%). Additionally, childhood-onset schizophrenic probands performed more poorly than adult-onset probands on the anticipatory saccade measure. This physiological evidence suggests that childhood-onset schizophrenia may be associated with increased genetic loading because of contributions of genetic risk from both parents.
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Abstract
Schizophrenia has long been associated with difficulties in visual tracking of a moving object. Deficits are most notable in tracking tasks that require inhibition of saccades during active smooth pursuit. In order to assess whether there is a more global problem in inhibition of other eye movement systems while the smooth pursuit system is active, this study examined cancellation of the vestibular ocular reflex (VOR). Cancellation of the VOR occurs in a task in which the subject is rotated while looking at a target that is also being rotated. This requires the subject to use the pursuit system to override the VOR, maintain the eye at a stable location within the orbit, and thus retain visual gaze upon the target. Thirteen individuals with schizophrenia and 15 normals were assessed during clockwise rotation at 60 degrees s-1. Schizophrenic subjects had a significant increase in counterclockwise slow velocity eye movements, suggesting an impaired ability to cancel the VOR. Cancellation of the VOR is thus another example of a breakthrough of an alternative eye movement system while the smooth pursuit system is active. Because of the simplicity of the VOR and its suitability for animal modeling, investigation of this phenomenon may delineate more precisely the mechanisms of visual tracking dysfunction in schizophrenia.
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Ross RG, Olincy A, Harris JG, Radant A, Adler LE, Freedman R. Anticipatory saccades during smooth pursuit eye movements and familial transmission of schizophrenia. Biol Psychiatry 1998; 44:690-7. [PMID: 9798072 DOI: 10.1016/s0006-3223(98)00052-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND Smooth pursuit eye movement (SPEM) abnormalities are a putative marker of genetic risk for schizophrenia. Accurate SPEM performance requires the subject to activate neural systems responsible for smooth pursuit tracking, while simultaneously suppressing activity of neurons responsible for saccadic movements that would move the eye ahead of the target. This study examined whether specific aspects of SPEM dysfunction cosegregate with genetic risk in parents of schizophrenic probands. METHODS Eighteen probands and their parents had SPEM recorded. Parents with an ancestral history of schizophrenia were hypothesized to be more likely than their spouses without such a history to carry a genetic risk for schizophrenia. RESULTS Ten families had a single parent with a positive ancestral history for schizophrenia. The frequency of anticipatory saccades, which were mostly small, and the fraction of total eye movement that they represented were the only measures that differentiated the more likely genetic carrier parents in these families from their spouses and age-matched normals. CONCLUSIONS Failure to suppress saccadic anticipation of target motion during smooth pursuit appears an aspect of SPEM dysfunction related to presumed genetic risk for schizophrenia.
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Abstract
Restoration of a patient's full range of motion, strength, and function are the primary goals of occupational and physical therapy. Immobilization of normal connective tissue leads to biochemical, biomechanical, and physiologic changes within a week. These changes are magnified in the presence of trauma or edema, and they may create permanent damage if not addressed swiftly and properly. This is best accomplished by applying specific types of stress to the involved and associated structures at optimal intervals during the rehabilitation process. Load must be applied at adequate intensity and duration to successfully affect the viscous property of connective tissue. This is necessary to effect permanent elongation of the restricted tissues. Early controlled motion is vital to prevent the negative changes associated with immobilization and to maintain normal viscoelasticity and homeostasis of connective tissue. Hand therapists must have a thorough understanding of the changes associated with injured structures. Only then can they provide optimal stress delivery to facilitate restoration of function.
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Olincy A, Ross RG, Young DA, Roath M, Freedman R. Improvement in smooth pursuit eye movements after cigarette smoking in schizophrenic patients. Neuropsychopharmacology 1998; 18:175-85. [PMID: 9471115 DOI: 10.1016/s0893-133x(97)00095-x] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This study examined whether schizophrenics' cigarette smoking normalized smooth pursuit eye movement abnormalities. Fifteen schizophrenic and 15 nonschizophrenic subjects abstained from their usual cigarette smoking for an average of 10 h. Their baseline performance during a constant velocity smooth pursuit task was then assessed. The subjects smoked as much as they desired in a 10-min period and then were retested immediately postsmoking, and 10 and 20 min later. Smooth pursuit gain and the percentage of total eye movement due to various saccadic subtypes were computed using infrared oculography and computerized pattern recognition software. After smoking, smooth pursuit gain increased and the percentage of total eye movements due to leading saccades decreased significantly in the schizophrenic patients. There were no changes in the gain or leading saccades of nonschizophrenic subjects after smoking. Nicotinic receptor dysfunction may be a candidate mechanism for smooth pursuit eye movement abnormalities in schizophrenia.
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Ross RG, Harris JG, Olincy A, Radant A, Adler LE, Freedman R. Familial transmission of two independent saccadic abnormalities in schizophrenia. Schizophr Res 1998; 30:59-70. [PMID: 9542789 DOI: 10.1016/s0920-9964(97)00133-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Difficulties with inhibiting inappropriate responses, i.e. disinhibition, and problems with spatial memory are both presumed to be a part of the phenotypic expression of the genetic risk for schizophrenia. Schizophrenic probands are impaired on saccadic eye movement tasks which require (a) response inhibition to prepotent stimuli and (b) generation of an accurate response to a remembered or calculated spatial location, but it is unknown how these deficits are inherited. Sixteen schizophrenic probands, their 32 parents, and two normal control groups completed a delayed oculomotor response and an antisaccade task. The parents with a positive ancestral family history for chronic psychosis (n = 8) were presumed to be more likely than their family history-negative spouses to be genetic carriers for schizophrenia. Probands and their positive family history parents had more failures of response inhibition than did normal control groups. However, it was the probands and their negative family history spouses who demonstrated impaired accuracy of the remembered- or antisaccades. Disinhibition may be closely tied to a specific genetic risk for schizophrenia. However, a second familial factor related to the maintenance or manipulation of spatial information may also contribute to the genetic risk of the full clinical disorder.
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Olincy A, Ross RG, Youngd DA, Freedman R. Age diminishes performance on an antisaccade eye movement task. Neurobiol Aging 1997; 18:483-9. [PMID: 9390774 DOI: 10.1016/s0197-4580(97)00109-7] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Tthe antisaccade eye movement task, which has been linked to frontal lobe function, presents a target in one visual field and asks subjects to move their eyes to the same location in the opposite field. The task requires inhibition of the reflexive prosaccade to the cue, initiation of the antisaccade to the opposite field, and visuo-spatial memory of the cue location. Forty-two subjects from 19-79 years of age performed this task and a control task, visually guided saccades to the cue itself, to determine which functions are affected by aging. The time to initiate antisaccades increased linearly with age at a rate greater than the time to initiate visually guided saccades. This difference suggests that the processing time to inhibit the incorrect movement to the cue is selectively increased with age. Older subjects also made more incorrect prosaccadic movements to the cue, a finding consistent with the loss of inhibitory processing capacity. The accuracy of movements did not change, which suggests that visuo-spatial memory is unaffected by aging.
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Ross RG, Hommer D, Radant A, Roath M, Freedman R. Early expression of smooth-pursuit eye movement abnormalities in children of schizophrenic parents. J Am Acad Child Adolesc Psychiatry 1996; 35:941-9. [PMID: 8768356 DOI: 10.1097/00004583-199607000-00022] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Disordered smooth-pursuit eye movements (SPEM) and, specifically, small anticipatory saccades that disrupt SPEM have been hypothesized to be a marker of genetic vulnerability to schizophrenia. This study compares SPEM in children of schizophrenic parents with normally developing control children to assess whether SPEM abnormalities are also present in a subset of at-risk children. METHOD With infrared oculography, SPEM was examined in 13 children of schizophrenic parents and 19 normally developing controls (aged 6 to 15 years). Measures of smooth-pursuit gain and root mean square error were used in addition to more specific measures of catch-up saccades and anticipatory saccades. RESULTS Children of schizophrenic parents differed from normally developing controls on gain and root mean square error, but not on catch-up saccades. Small anticipatory saccades were significantly more frequent in the at-risk group. The percentage of total eye movements due to anticipatory saccades identified 54% of the at-risk group (compared with none of the control group) as performing more than two standard deviations above (worse than) the control mean. CONCLUSIONS The presence of increased anticipatory saccades is evidence for an oculomotor dysfunction that may be a phenotype of the genetic risk for schizophrenia, expressed years prior to the possible development of clinical illness.
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Ross RG, Radant AD, Young DA, Hommer DW. Saccadic eye movements in normal children from 8 to 15 years of age: a developmental study of visuospatial attention. J Autism Dev Disord 1994; 24:413-31. [PMID: 7961328 DOI: 10.1007/bf02172126] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This cross-sectional study used saccadic eye movements, as measured by infrared occulography, to assess several aspects of visuospatial attention in normal children ages 8-15 years. Saccadic latency (a global measure of the ability to shift visuospatial attention), the ability to suppress extraneous saccades during fixation, and the ability to inhibit task-provoked anticipatory saccades all improve with age. However, the pattern of development differs for different tasks; saccadic latency shortens at a linear rate across the age range 8-15 years, while the capacity to inhibit anticipatory saccades matures by 12-13 years of age, and the ability to suppress saccades matures by 10 years of age. Analyses of age-related changes in oculomotor measures of attention may provide a novel approach in the study of children with attentional difficulties.
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Ross RG, Hommer D, Breiger D, Varley C, Radant A. Eye movement task related to frontal lobe functioning in children with attention deficit disorder. J Am Acad Child Adolesc Psychiatry 1994; 33:869-74. [PMID: 8083144 DOI: 10.1097/00004583-199407000-00013] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Attention-deficit hyperactivity disorder (ADHD) has been postulated to be related to dysfunction of the prefrontal cortex. In the oculomotor delayed response task, a subject is cued as to where he or she should look (shift visual gaze to) but must delay a short period and then shift gaze to the location where the cue previously existed but no longer exists (a memory-guided saccade). Dependent measures from this task provide information on three functions tentatively tied to prefrontal cortex functioning: the ability to inhibit response (during the delay period), preparation of motor response (inversely tied to the latency of shifting visual gaze), and accuracy of working visuospatial memory (accuracy of the memory-guided saccade). METHOD Thirteen children with ADHD and 10 normal controls, aged 9 to 12 years, were tested using an 800-msec delay period. RESULTS Children with ADHD showed, relative to normal controls, deficits on inhibiting response during the delay period but no differences in latency (preparation of motor response) or accuracy of visuospatial memory. CONCLUSIONS These results support the hypothesis that the primary deficit in ADHD is difficulty in inhibition of response. This deficit may be associated with pathology located outside the dorsolateral prefrontal cortex.
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Ross RG, Radant AD, Hommer DW. A developmental study of smooth pursuit eye movements in normal children from 7 to 15 years of age. J Am Acad Child Adolesc Psychiatry 1993; 32:783-91. [PMID: 8340299 DOI: 10.1097/00004583-199307000-00012] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVE To examine age-related changes in smooth pursuit tracking. METHOD Using infrared occulography, smooth pursuit eye movements are examined in 53 normal 7- to 15-year-old children during 6 degrees and 12 degrees/second visual pursuit. In addition to smooth pursuit gain and saccadic frequency, measures of mean amplitude per second are introduced to facilitate comparison across age and target speed. RESULTS The 6 degrees/second task is found to be easier than the 12 degrees/second task. Age is correlated with smooth pursuit system performance but not saccadic system performance during 12 degrees/second pursuit. No measure correlates with age during 6 degrees/second pursuit. CONCLUSIONS Eye movements improve as children age. The future use of smooth pursuit eye movements to study children and adolescents with and at risk for schizophrenia must control for developmental changes.
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Ross RG. Educational Strategies to Improve Preventive Care: Improving the performance of periodic health examinations. CANADIAN FAMILY PHYSICIAN MEDECIN DE FAMILLE CANADIEN 1992; 38:341-345. [PMID: 21221260 PMCID: PMC2145424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Performance of the periodic health examination and related preventive maneuvers has been shown to be suboptimal by both residents and faculty. Research into methods of improving performance of the periodic health examination shows that a number of methods are available to remedy the lack of effective delivery of prevention by health professionals. An educational prescription based on a literature review is outlined. Specific educational objectives are discussed.
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Davidson DW, Ross RG. Book reviews. J INCL PHENOM MACRO 1985. [DOI: 10.1007/bf00658867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ross RG, Andersson P, Bäckström G. Effects of H and D order on the thermal conductivity of ice phases. J Chem Phys 1978. [DOI: 10.1063/1.436309] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Ross RG, ANDERSSON P, BÄCKSTRÖM G. Thermal conductivity of allotropic modifications of ice. Nature 1976. [DOI: 10.1038/259553a0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ross RG, Hamlin SA. INFLUENCE OF NUTRIENTS ON PERITHECIAL PRODUCTION OF VENTURIA INAEQUALIS (CKE.) WINT. ACTA ACUST UNITED AC 1965. [DOI: 10.1139/b65-108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitrates, urea, and amino acids were suitable sources of nitrogen, within a narrow range of concentrations, for perithecial development of Venturia inaequalis in a synthetic medium. Ammonium sulfate was not. The concentration of amino acid nitrogen required to inhibit the formation of perithecia varied with the amino acid. Zinc appeared to stimulate perithecial production. Amino acids differed in the nitrogen concentrations required to inhibit formation of perithecia. Perithecia developed in low concentrations of arabinose, glucose, sucrose, lactose, and maltose but did not develop in xylose, ribose, fructose, mannose, or galactose. The disaccharides were particularly suitable. Thiamine appeared to be necessary for ascospore formation.
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Ross RG, Hamlin SA. PRODUCTION OF PERITHECIA OF VENTURIA INAEQUALIS (CKE.) WINT. ON STERILE APPLE LEAF DISCS. ACTA ACUST UNITED AC 1962. [DOI: 10.1139/b62-059] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Perithecia of Venturia inaequalis were produced in vitro on apple leaf discs which had been sterilized in propylene oxide and then placed on water agar, potato-dextrose agar, or potato-dextrose agar supplemented with apple leaf decoction. The discs were inoculated with a drop of a conidial suspension of two sexually compatible strains of V. inaequalis, incubated at room temperature for 2 weeks, and then grown at 8 °C for 4 to 5 months.Perithecia were also produced on sterile leaf discs placed on perlite, vermiculite, sand, filter paper, or glass rings in screw-cap vials with distilled water added to supply moisture. Using perlite, perithecia were developed on discs of green and fallen apple leaves collected from the orchard at intervals during the summer and fall and on leaves at different stages of development from trees growing in the greenhouse. Few perithecia developed on newly unfolded leaves from the latter unless the leaves were leached before inoculation. Perithecia developed on sterile discs from green apple leaves of varieties with varying degrees of susceptibility to V. inaequalis and on green leaf discs of the pear variety Kieffer. Perithecia production was most abundant at 4 °C and no perithecia were produced at or above 15 °C.
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Ross RG. THE EFFECT OF CERTAIN ELEMENTS, WITH EMPHASIS ON NITROGEN, ON THE PRODUCTION OF PERITHECIA OF VENTURIA INAEQUALIS (CKE.) WINT. ACTA ACUST UNITED AC 1961. [DOI: 10.1139/b61-061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Various elements were tested for their effect on the formation of perithecia of Venturia inaequalis. Apart from nitrogen the elements tested had little effect on the formation of perithecia except at relatively high concentrations. Perithecia did not form in media containing low concentrations of nitrogen and this was influenced by the source of nitrogen and by the cation present in nitrate salts. Perithecial initials developed in higher nitrogen concentrations than perithecia. Nitrogen added 9 weeks after mating of two lines of the fungus prevented the formation of perithecia.Results were difficult to reproduce in a potato-dextrose apple leaf decoction medium but reproducible results were obtained in a synthetic medium.
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