Verbal versus manual reaction time in schizophrenic and normal subjects

On the assumption that schizophrenia involves a disturbance in interpersonal relations it is predicted that the verbal reaction time responses of schizophrenic subjects should have disproportionately longer latencies than manual reaction time responses as compared to normal subjects. Using data presented in this Journal by Venables and O'Connor (1959). the prediction is confirmed for patients whose reaction time level is relatively fast, but not in those with relatively slow reaction times. Several possible mechanisms are postulated to account for the results, including differential reinforcement, amount of practice, and complexity of verbal responses, and degree of pathology of the patients.     

Event rate and reaction time performance in ADHD: Testing predictions from the state regulation deficit hypothesis using an ex-Gaussian model

According to the state regulation deficit (SRD) account, ADHD is associated with a problem using effort to maintain an optimal activation state under demanding task settings such as very fast or very slow event rates. This leads to a prediction of disrupted performance at event rate extremes reflected in higher Gaussian response variability that is a putative marker of activation during motor preparation. In the current study, we tested this hypothesis using ex-Gaussian modeling, which distinguishes Gaussian from non-Gaussian variability. Twenty-five children with ADHD and 29 typically developing controls performed a simple Go/No-Go task under four different event-rate conditions. There was an accentuated quadratic relationship between event rate and Gaussian variability in the ADHD group compared to the controls. The children with ADHD had greater Gaussian variability at very fast and very slow event rates but not at moderate event rates. The results provide evidence for the SRD account of ADHD. However, given that this effect did not explain all group differences (some of which were independent of event rate) other cognitive and/or motivational processes are also likely implicated in ADHD performance deficits.     

Age-related differences in reaction time task performance in young children

Performance of reaction time (RT) tasks was investigated in young children and adults to test the hypothesis that age-related differences in processing speed supersede a “global” mechanism and are a function of specific differences in task demands and processing requirements. The sample consisted of 54 4-year-olds, 53 5-year-olds, 59 6-year-olds, and 35 adults from Russia. Using the regression approach pioneered by Brinley and the transformation method proposed by Madden and colleagues and Ridderinkhoff and van der Molen, age-related differences in processing speed differed among RT tasks with varying demands. In particular, RTs differed between children and adults on tasks that required response suppression, discrimination of color or spatial orientation, reversal of contingencies of previously learned stimulus-response rules, and greater stimulus-response complexity. Relative costs of these RT task differences were larger than predicted by the global difference hypothesis except for response suppression. Among young children, age-related differences larger than predicted by the global difference hypothesis were evident when tasks required color or spatial orientation discrimination and stimulus-response rule complexity, but not for response suppression or reversal of stimulus-response contingencies. Process-specific, age-related differences in processing speed that support heterochronicity of brain development during childhood were revealed.     

Auditory and visual reaction time in adults during long performance

Better to understand the relation of auditory to visual reaction time (RT) tasks during a long period (320 min.) as well as the evolution of these performances along time, 24 subjects were tested. RT tasks were delivered at 10-min. intervals for 320 min. Correlations between auditory and visual RTs and cross-correlation functions were calculated. Our results confirmed their association, which was maintained throughout the experiment. There were no significant differences in the mean RT by sex or time of day; however, differences were found for the trend slope between type of stimulus and sex.     

Serial reaction time performance following right parietal lobe damage

The serial reaction time task (SRT) is used to assess implicit sequence learning. Neuroimaging studies implicate parietal involvement; however, the necessity of this area is unclear. We tested six unilateral right parietal patients and compared their performance to matched controls. Both groups showed similar levels of learning and explicit awareness. Two patients with the largest lesions extending into either frontal or cerebellar regions showed no learning. These data suggest that implicit sequence learning can occur despite damage to the right parietal lobe.     

No vigilance deficit found in either young schizophrenic or ADHD subjects

Vigilance deficits have been found in both schizophrenic and ADHD subjects. The two patient groups have never been directly compared on any vigilance measure, however. In the present study 20 early-onset schizophrenics were compared to 20 ADHD adolescents on a Degraded Stimulus Continuous Performance Test (DS-CPT). A comparison group of 30 normal adolescents was also included. Results showed no significant differences between the three groups on any of the DS-CPT measures. Different hypotheses are put forth to explain the findings, among them that the task may be insensitive to identifying sustained attention deficits in adolescent populations.     

Ultradian cyclicity in auditory and visual reaction time during long performance

24 subjects were tested to check the hypothesis proposed by Kleitman about a "basic rest-activity cycle". Reaction time tasks were delivered at 10-min. intervals for 320 min. Spectral density function analyses showed no significant periods within the limits of the cycle. Discussion concerns fulfilling assumptions of spectral analysis and Fisher's test.     

Speed vs reaction time as a measure of cognitive performance

Choosing mean reaction time or mean speed (it’s reciprocal) as the dependent variable in cognition experiments is frequently done for no better reason than convenience. It is shown that sometimes this choice is crucial in determining the order of the obtained effects. Moreover, it is proved that when the order of the effects is dependent upon the choice of the transformation, the assumption of homogeneity of variance is not true and hence ANOVA may not be justified. Alternative strategies are proposed to deal with this data-related problem.     

Attentional network task performance in schizophrenic patients

Several studies have researched the attentional functioning of schizophrenic patients by means of the Attentional Network Test. The present work reviews these studies and assesses the clinical relevance of their results. Both the reviewed data and our own results suggest that the Attentional Network Test does not provide a clear-cut discrimination of the attentional profile of schizophrenic patients from a clinical point of view. However, after classifying patients according to their psychotic symptoms, it became evident that positive syndrome patients are less efficient at tasks that tap the orientation network.     

Neurobehavioral deficit and computed tomographic abnormalities in three samples of schizophrenic patients

Recent reports have suggested that schizophrenics show brain abnormalities as reflected on computed tomography (CT Scan). We present data on three groups of schizophrenic patients which replicate our original report of this phenomenon with associated neuropsychological test results. The over-all evidence for an increased rate of neuropsychological abnormalities and related CT structural anomalies in groups of schizophrenics in several studies is robust. The biological dynamics, cause-effect relationships, and clinical applicability of this phenomenon in the individual case, however, are far from clear. Diagnostic agreements between behavioral and structural abnormalities should simultaneously sound a note of clinical caution and stimulate further study.     

Effector-specific visual information influences kinesthesis and reaction time performance in Parkinson's disease

Twelve patients diagnosed with idiopathic Parkinson's disease and 11 age-matched control participants performed a continuous bimanual wrist flexion-extension tracking task while vision of their hands was manipulated. Participants were required to match the frequency and amplitude of movements of 1 limb that was driven at 0.6 Hz by a torque motor by actively moving the contralateral limb. In half the trials, the more affected limb (subdominant for controls) was driven, and in the other half, the less affected limb (dominant for controls) was driven. Vision of both hands, vision of the driven hand only, vision of the active hand only, or no vision of the hands was allowed. Simple and probe reaction times were assessed. Parkinson's disease patients performed the tracking task to a reasonable level of temporal and spatial accuracy as compared with control participants in terms of hand phasing and root mean square error. Patients demonstrated a marked posture deviation (toward flexion), which was exaggerated when the less affected limb was active. Amplitude deviations were smaller in both groups when the less affected (dominant) limb was active and when participants had vision of the driven hand. Overall, patients delivered slower responses in both simple and probe conditions. Reaction times of Parkinson's disease patients who were allowed vision of only the active hand were longer than were those of patients in all other visual conditions, whereas visual conditions did not affect the reaction times of control participants. The authors conclude that central demands increase when movement regulation must be based solely on kinesthetic information and when vision directs attention away from the most relevant source of kinesthetic information.