Traumatic brain injury, aging and reaction time

The effects of traumatic brain injury (TBI) and aging were compared on tests of simple and complex reaction time (RT). Simple RT was not significantly affected by aging or TBI. TBI patients, however, tended to be slower on Simple RT tasks, and had a larger standard deviation. Individuals over age 60 and patients of any age with TBI demonstrated slower RT with choice RT tests. In addition, both groups (those over 60 and TBI patients) were less able than other groups to inhibit the processing of redundant information. For the TBI patients, this occurred primarily on reassessment. These results suggest that the deficit in both aging and TBI is not only a generalized neuronal slowing but a more specific impairment in attentional control processes, exhibited as a deficit in focused attention.     

Reaction Time Indicators of Attention Deficits in Closed Head Injury

The nature of deficits in attention in closed head injury (CHI) was studied by three reaction time (RT) paradigms given to 20 patients who had a CHI 2 or more years previously and to 25 controls. We studied the effects of temporal uncertainty by varying the length and regularity of the preparatory interval, the effects of stimulus modality uncertainty on simple RT to tones and lights, and the effects of response selection in choice RT. The CHI group showed slower and more variable RT than controls under all conditions. In addition, a long preparatory interval on the preceding trial retarded RT more in the CHI group, and they showed greater effects of stimulus modality uncertainty. Both of these findings suggest a difficulty in shifting attention to unexpected stimuli. These greater effects on RT of variations of attention or preparation in CHI may account for their greater within-subject variability possibly due to frontal lobe damage.     

Motivation and Neuropsychological Test Performance Following Mild Head Injury

Effect of motivation on neuropsychological test performance in mild head injury was assessed. Motivation was measured using the Portland Digit Recognition Test. Three groups were compared: (a) mild head injury, financial incentives, good motivation; (b) mild head injury, financial incentives, poor motivation; (c) moderate/severe head injury, good motivation. The neuropsychological battery included measures of sensory function, motor function, attention, intelligence, reasoning, and memory. Mild head injury well motivated patients performed significantly better than the other two groups on some tests. Mild head injury poorly motivated individuals and moderate-severe head injury patients were indistinguishable on many tests. Consistent with previous reports, tactile sensory (finger recognition and Fingertip Number Writing Perception) and recognition memory (Rey Auditory Verbal Learning) tasks were identified as clinically useful measures of poor motivation. On these measures mild head injury well motivated examinees performed no better than moderate-severe patients, with both groups superior to mild head injury poorly motivated examinees. Sensitivity and specificity data are reported. Our measures of tactile sensation and verbal recognition memory were more affected by motivation than by the severity of head injury.     

Motivation and neuropsychological test performance following mild head injury

Effect of motivation on neuropsychological test performance in mild head injury was assessed. Motivation was measured using the Portland Digit RecognitionTest. Three groups were compared: (a) mildhead injury, financial incentives, good motivation; (b) mild head injury, financial incentives, poor motivation; (c) moderate/severe head injury, good motivation. The neuropsychological battery included measures of sensory function, motor function, attention, intelligence, abstract reasoning, and memory. Mild head injury well motivated patients performed significantly better than the other two groups on some tests. Mild head injury poorly motivated individuals and moderate-severe head injury patients were indistinguishable on many tests. Consistent with previous reports, tactile sensory (finger recognition and Fingertip Number Writing Perception) and recognition memory (Rey Auditory Verbal Learning) tasks were identified as clinically useful measures of poor motivation. On these measures mild head injury well motivated examinees performed no better than moderate-severe patients, with both groups superior to mild head injury poorly motivated examinees. Sensitivity and specificity data are reported. Our measures of tactile sensation and verbal recognition memory were more affected by motivation than by the severity of head injury.     

Effects of unilateral pallidotomy on voluntary movement, and simple and choice reaction times in Parkinson's disease.

We studied the effects of unilateral pallidotomy on motor execution and reaction times in patients with moderately advanced Parkinson's disease (PD). Twelve consecutive patients (7 men, 5 women; all right-handed) underwent left-side microelectrode-guided pallidotomy. In addition to clinical rating, reaction time (RT) tests and repetitive movements of the contralesional hand/arm were carried out at baseline and 2 to 3 months after surgery while patients were on optimal medical regimens (on period). The initiation time in both simple reaction time (SRT) and choice reaction time (CRT) improved significantly after pallidotomy (P < 0.05), whereas no effect was observed on the choice processing time, which was calculated by subtracting the mean value of the onset of SRT from that of CRT. Pallidotomy resulted in significant improvement of repetitive movements such as hand pronation/supination and finger-tapping (P < 0.002, P < 0.005, respectively). Improvements in RT tests and repetitive movements suggest that pallidotomy may enhance attention and motor function. These effects are probably mediated through the pallido-thalamic-cortical neural circuitry.     

Attentional-inhibitory control and social-behavioral regulation after childhood closed head injury: do biological, developmental, and recovery variables predict outcome?

Attentional-inhibitory control and social-behavioral regulation are two outcome domains commonly impaired after childhood closed head injury (CHI). We compared neuropsychological tests of attentional-inhibitory control (vigilance, selective attention, response modulation) and social discourse and intentionality (inferencing, figurative language, and speech acts) with parent ratings of attention and behavioral regulation in relation to four injury-related variables: age at CHI, time since CHI, CHI injury severity, and frontal lobe injury moderated by CHI severity. Participants were 105 school-aged children in the chronic stage of CHI, divided into mild, moderate, and severe injury severity groups, and further subdivided according to frontal lobe injury. Outcome indices were imperfectly correlated in the group as a whole, although several relations between neurocognitive tests and parent ratings were observed within CHI subgroups. Different domains of cognitive function had different predictors. For attentional-inhibitory control, age at injury and time since injury were most predictive of outcome; for social discourse, predictors were injury severity and frontal lobe injury moderated by injury severity. Variability in cognitive outcome after childhood CHI is not random, but appears related to age, time, and biological features of the injury.     

ERPs and behavioural indices of long-term preattentive and attentive deficits after closed head injury

Attentional deficits are often reported even years after sustaining a closed head injury (CHI). Disturbance of cognitive attentional functions following CHI has been documented in both behavioural and event-related brain potential (ERP) studies. Recently, the possibility that the sequelae of CHI extend to preattentive processes of attention has been pointed out. We used a paradigm that makes it possible to assess simultaneously the processing of relevant information and involuntary mechanisms of attention to gain further insight in this matter. Eleven patients with CHI greater than 1 year post-trauma and 14 age-matched control subjects were engaged in the performance of a continuous visual reaction time (RT) discrimination task while ignoring streams of auditory task-irrelevant stimuli. The main characteristic in the paradigm was that all visual stimuli were shortly preceded by an auditory stimulus, which could be a repeated (90%) or a different (deviant) tone. We measured performance on the discrimination task, and ERP indices of preattentive (mismatch negativity MMN) and attentive information processing (P1, N165, P3b). In relation to control subjects, CHI patients showed an attenuation of the MMN evoked by the deviant-tone. In response to the visual stimuli, CHI patients showed a delay of P1, and a reduction of the N165 and P3b components. Moreover, they had slower RT and missed more responses in a visual discrimination task. These results indicate both preattentive and attentive deficits, which is consistent with the typical diffuse axonal injury (DAI) resulting after CHI.     

Impaired recognition memory after head injury.

A continuous recognition memory task employing 120 line drawings of familiar stimuli was administered to patients recovering from closed head injury of varying severity and control patients. Mildly injured patients obtained significantly more correct responses, and higher memory sensitivity (d') values than moderately and severely injured patients who performed similarly. The measure of response criterion, c, was significantly lower in patients with injury of moderate severity when compared to mildly injured cases and control patients. Controls and mildly injured patients did not differ in their performance. In general, the total correct responses most impressively differentiated head injured patients with measurable coma duration as more than two-thirds had scores below the control group. Group differences in hits, false alarms and misses were examined also. Age and education, skull fracture, and hematoma were generally unrelated to any of the measures, whereas coma duration was significantly related to most measures of mnemonic efficiency.     

Reaction time and rapid serial processing measures of information processing speed in multiple sclerosis: complexity, compounding, and augmentation

Information processing speed is frequently cited as the primary cognitive domain impacted by multiple sclerosis (MS) and is usually evaluated with reaction time (RT) or rapid serial processing (RSP) measures. The present study compared the efficacy of RT and RSP measures to distinguish between patients with MS (N = 42) and healthy controls (N = 40). The RT measure was patterned after the Computerized Tests of Information Processing and included measures of simple, choice, and semantic RT. The RSP measures consisted of the Symbol Digit Modalities Test (SDMT) and the Stroop Test. Substantial differences in information processing speed between patients and controls were found on all tests, with slightly larger effect sizes for RSP measures than RT measures and for the SDMT than the Stroop Test. Binary logistic regression analyses showed RSP measures performed better than RT measures at distinguishing patients from controls, and likewise, the SDMT score performed better than the scores derived from the Stroop Test. Results are discussed in the context of three effects associated with common measures of processing speed: complexity, compounding, and augmentation.     

Normal human subjects with slow reaction times and larger time estimations after waking have diminished delta sleep

A sample of 42 healthy young male human subjects was submitted to whole night polysomnography and attention performance tests upon awakening (simple visuomotor reaction time, RT, and time estimation, TE). In order to test whether performance is related to specific sleep parameters, the 15 fastest subjects (mean = 210 msec) and 15 slowest subjects (mean = 357 msec) in RT were compared in their TE and sleep parameters. Fast subjects were more precise in the estimation of 10 sec intervals (9.89; S.E. = 0.23 sec) than slow subjects (10.73; S.E. = 0.32). Slow subjects had significantly less delta sleep (mean = 73 min) than fast subjects (100 min, P less than 0.01) and otherwise similar sleep parameters. It can be suggested that attention after awakening is related to the amount of delta sleep in the night.     

Third, fourth, and sixth cranial nerve palsies following closed head injury.

BACKGROUND: The relationship between the circumstances and severity of closed head injury (CHI) and the clinical and imaging features of cranial nerve 3, 4, and 6 palsies has not been rigorously addressed in a large study. METHODS: Retrospective chart review of 210 consecutive patients with CHI examined at a single tertiary care center from 1987 to 2002. Patients were located by searching the ophthalmology inpatient consultation and neuro-ophthalmology outpatient databases and hospital emergency room billing codes for a diagnosis of traumatic 3, 4, or 6 cranial nerve palsy (Cranial Nerve Injury Group) and a diagnosis of CHI without traumatic 3, 4, or 6 nerve palsy (Control Group). The Cranial Nerve Injury Group was then subdivided into two groups: those with injuries to an individual cranial nerve and those with multiple (including bilateral) cranial nerve injuries. Comparisons between groups were based on age, gender, type of accident, Glasgow Coma Scale (GCS), documented loss of consciousness (LOC), type of ocular injury, presence of systemic injury, need for rehabilitation, physical therapy and cognitive scores, and imaging features. RESULTS: The Cranial Nerve Injury Group had a significantly higher severity of head injury, more CT abnormalities, and worse short-term neurologic outcomes as compared with the Control Group. These trends were also found when each cranial nerve injury subgroup was compared with the Control Group. Those with cranial nerve 3 palsy had the most severe head injury; those with cranial nerve 4 palsy had an intermediate level of head injury; and those with cranial nerve 6 palsy had the lowest level of head injury. There were no consistent associations between the location of the imaging abnormalities and which cranial nerve was damaged. CONCLUSIONS: CHI with palsy of an ocular motor nerve was more severe than CHI without ocular motor nerve palsy, as measured by the GCS, intracranial and skull imaging abnormalities, and a greater frequency of inpatient rehabilitation. Palsy of cranial nerve 3 was associated with relatively more severe CHI than was palsy of cranial nerves 4 or 6. The location of the imaging abnormalities did not correlate with a particular cranial nerve injury.     

Multiple frontal systems controlling response speed

This study evaluated a model of attention that postulates several distinct component processes, each mediated by specific neural systems in the human frontal lobes. A series of reaction time (RT) tests (simple, choice, and prepare) examined the hypothesis that different attentional processes are related to distinct regions within the frontal lobes. These tests were given to 38 patients with frontal lesions and 38 age-matched control subjects. Lesions were localized both by general regions (superior medial, inferior medial, left and right lateral) and by individual architectonic areas. Lesions in the superior medial (SM) frontal lobes, particularly involving areas 24 and 32 on the right, were associated with slow RT in all tests and with failure to decrease RT after a warning signal. Lesions in the right lateral (RL) frontal lobe, centred in area 9/46v, prevented the decrease in RT with increasing foreperiod that was seen in normal subjects and in patients with lesions elsewhere in the frontal lobes. The ability to energize a response for rapid RT, either generally or specifically following a warning stimulus, is sensitive to lesions of the right SM. Monitoring of stimulus occurrence and response behaviour in order to enhance the speed of response to upcoming stimuli is sensitive to RL lesions.     

Monitoring information processing efficiency after stroke or head injury: A comparison of four computerised tests for use in single case experiments

Abstract

Single case experiments on cognitive rehabilitation can only be valid if adequate methods of monitoring cognitive change are developed. The sensitivity and reliability of four computer-based tests of information processing efficiency (continuous choice reaction time, visual tracking, memory for pairs, and critical flicker fusion) were compared. Performance of 16 left hemisphere stroke patients and 17 patients with severe closed head injury was compared with age-matched controls. The reaction time task proved the most useful in detecting effects of brain damage in both groups and showing good test-retest reliability.     

Covert orientation of visual attention after closed head injury.

The ability to orient visual attention covertly was studied in 11 patients who had suffered a moderate or severe closed head injury (CHI) at least 1 year previously. Their performance was compared to nine matched controls using a cued reaction time (RT) task which measured the RT benefit of valid directional cueing and the RT cost of miscueing. The CHI and control groups did not differ in overall RT. Relative to controls, the CHI group showed normal cost but hardly any benefit, indicating that the normal capacity to pre-align attention with a cued location was impaired.     

Neuropsychological and information processing deficits following mild traumatic brain injury.

Neuroradiological and neuropathological investigations have found evidence of diffuse brain damage in the frontal and temporal lobes, corpus callosum, and fornices in patients who have sustained a mild traumatic brain injury (TBI). However, neuropsychological assessments of these patients do not typically target many of the subtle information processing deficits that may arise from diffuse damage involving the frontotemporal regions of the brain as well as white matter pathology, including the corpus callosum. Consequently, we have a limited understanding of the deficits that may be attributable to temporary or permanent disruptions to these functional pathways. This study assessed a group of mild TBI patients (N = 40) and a matched control group (N = 40) on a number of standard neuropsychological tests of selective and sustained attention, verbal and non-verbal fluency, and verbal memory. In addition, reaction time (RT) tasks, requiring both the inter- and intra-hemispheric processing of visual and tactile information, were used to assess the functional integrity of the tracts that are likely to be affected by diffuse damage. In the 1st month after sustaining their injury, the mild TBI group demonstrated deficits in attention, non-verbal fluency, and verbal memory. They also demonstrated slower visual and tactile RTs, with the visual RTs of mild TBI patients being more affected by increased task difficulty and the need to transfer information across the corpus callosum, than did their matched controls.     

Emotional, neuropsychological, and organic factors: their use in the prediction of persisting postconcussion symptoms after moderate and mild head injuries.

BACKGROUND--After mild and moderate head injuries a range of postconcussion symptoms (PCS) are often reported by patients. Both organic and psychogenic factors can contribute to these. Full recovery from PCS usually occurs within three months of the injury. A significant minority, however, continue to experience symptoms beyond this time. To date, no means of identifying these patients early after injury has been reported. This study investigates whether a combination of neuropsychological, emotional, and traditional measures of severity of head injury taken early after the injury can help predict severity of PCS three months after injury. METHODS--50 patients with mild or moderate head injury had a range of measures administered at 7-10 days after injury. These included three tests of divided attention, a PCS rating scale-the Rivermead postconcussion symptoms questionnaire (RPQ), the hospital anxiety and depression scale (HADS), the impact of event scale (IES), and post-traumatic amnesia. An RPQ was then completed by all patients three months after injury. RESULTS--Stepwise multiple regression analysis was performed with the RPQ score at three months as the dependent measure. A combination of eight of the scores from the early measures gave a multiple correlation coefficient of R = 0.86 accounting for 74% of the variance in RPQ scores. The most predictive individual measures were the HADS and IES. Regression analysis with RPQ score at 7-10 days as dependent measure showed that 10 of the scores gave a coefficient of R = 0.84 accounting for 71% of the variance. CONCLUSIONS--A combination of measures may significantly aid the prediction of persistent PCS. Five measures: HADS, post-traumatic amnesia, SOMC, PASAT, and RPQ are recommended for their predictive value and clinical utility. Independent cross validation studies are required before these results can be generally applied. They do, however, provide valuable indications regarding those measures that are most likely to demonstrate utility.     

Spatial orienting of attention: a study of reaction time during pointing movement]

AIM: The aim of this study was to investigate how advance information both explicit and implicit provided prior to movement may affect the spatial orientation and the internal attention control processes in normal adult subjects. The originality of this work compared to the test of Posner, lies essentially in the methodology used to study the attentional systems. The use of three procedures of reaction time (RT) allowed us to study the setting concerned of the specific and non-specific components of the attention in the motor preparation. By associating of these three procedures of RT, we have evaluated the effects of the explicit and implicit components of advance information on motor preparation. The use of advance information to the movement requires the implication of the attentional systems. MATERIAL AND METHODS: Experiments were carried out using a simple reaction time (RT) procedure involving the use of an orientation cue and two choice reaction time situations: one with a neutral preparatory cue and one with a priming cue giving the likelihood of the preparatory stimulus (S1) being compatible with the imperative stimulus (S2). The mechanisms underlying the subjects' vigilance and the orientation of their attention were studied by assessing the effects on their reaction times of the preparatory signal and those of the cue giving the likelihood of S1 and S2 being compatible. The preparatory signal was designed to explicitly attract the subjects' attention towards the position of the forthcoming pointing target, whereas the cue giving the compatibility between S1 and S2 was intended to mobilize the subject's attention more implicitly. Prior to performing the pointing movement towards a visual target, the subjects' attention was therefore mobilized by the advance information containing two components: the explicit information about the position of S1 and the implicit information about the probability of S1 and S2 being compatible. RESULTS AND CONCLUSION: The results obtained here on 17 normal adult subjects show that the subjects significantly improved their RTs by using the explicit component of the information provided. The implicit information available was also used in the choice reaction situations: a priming effect was found to occur, which resulted in the shortening of the primed "compatible cue" reaction times in comparison with the "neutral cue" reaction times, and in the correlation which was found to exist between the reaction time performances and the degree of compatibility between the preparatory signal and the imperative signal. These results suggest that various components of the attentional system may participate in processing the advance information provided prior to the movement in reaction time tasks of the kind used here. The explicit information provided prior to the movement may mobilize the subject's vigilance and spatially orients his attention; whereas the implicit information available may rather subserve the internal control of the subject's attention.     

Symptom-specific attentional bias to threatening stimuli in obsessive-compulsive disorder

ObjectiveThere is mixed evidence as to whether patients with obsessive-compulsive disorder (OCD) have excessive attentional engagement and emotional response to OCD-related stimuli in the environment. Here we investigate the occurrence of an attentional bias toward specific OCD-related stimuli and its relationship with obsessive-compulsive symptom dimensions.MethodsForty-eight patients with OCD participated in an attentional bias task containing OCD- and non–OCD-related stimuli and had their performance compared with that of 24 age-, sex-, and education-matched healthy control subjects. Severity of obsessive-compulsive and comorbid depressive symptoms was assessed using the Obsessive-Compulsive Inventory–Revised and the Beck Depression Inventory, respectively.ResultsAlthough there were significant and almost significant group effects on the reaction time (RT) toward OCD- and non–OCD-related figures, respectively, no difference between patients with OCD and controls was noted with regard to RT toward OCD-related figures minus RT toward non–OCD-related figures. Nevertheless, within the OCD group, partial correlational analysis controlled for age and severity of depression unveiled positive correlations between (1) obsessional symptoms and RT toward checking-related pictures and (2) ordering symptoms and RT toward ordering-related pictures.ConclusionsThe positive correlations between RT to content-specific stimuli and the severity of corresponding obsessive-compulsive symptoms suggest that patients with OCD experience difficulty in disengaging attention from personally salient stimuli.     

Attention, cognition, and motor perseveration in adolescents at genetic risk for schizophrenia and control subjects.

Twenty-three offspring of schizophrenic parents (mean age = 12.1 years, SD = 3.2) and 61 adolescent control subjects (mean age = 12.3 years, SD = 3.3) were compared in their performance of the following psychometric tests: simple reaction times (RTs), warned RTs in a monomodal and cross-modal design, d2 concentration test, a motor perseveration test, and a cognitive performance measure (Wechsler Intelligence Scale). The results were validated in a second analysis in which a subgroup of the control subjects were matched to the high-risk subjects for the following characteristics: age, gender, education, and environmental background. Significant deficits were found in the high-risk group in tests that required sustained attention and information processing under high perceptual load (RT measures and d2 concentration test). Deficits were particularly prominent for the processing of visual stimuli; sensory incongruence might also have been a contributor to this deficit. The attentional dysfunction of high-risk subjects might explain their tendency to show less structured behavior and distractibility as reflected by their higher entropy scores in a motor perseveration test. Cognitive evaluation showed a significant deficit in the high-risk group, primarily as reflected in the verbal IQ score.     

A novel approach to sports concussion assessment: Computerized multilimb reaction times and balance control testing

Introduction: Mild traumatic brain injuries (MTBI) or concussions often result in problems with attention, executive functions, and motor control. For better identification of these diverse problems, novel approaches integrating tests of cognitive and motor functioning are needed. The aim was to characterize minor changes in motor and cognitive performance after sports-related concussions with a novel test battery, including balance tests and a computerized multilimb reaction time test. The cognitive demands of the battery gradually increase from a simple stimulus response to a complex task requiring executive attention. Method: A total of 113 male ice hockey players (mean age = 24.6 years, SD = 5.7) were assessed before a season. During the season, nine concussed players were retested within 36 hours, four to six days after the concussion, and after the season. A control group of seven nonconcussed players from the same pool of players with comparable demographics were retested after the season. Performance was measured using a balance test and the Motor Cognitive Test battery (MotCoTe) with multilimb responses in simple reaction, choice reaction, inhibition, and conflict resolution conditions. Results: The performance of the concussed group declined at the postconcussion assessment compared to both the baseline measurement and the nonconcussed controls. Significant changes were observed in the concussed group for the multilimb choice reaction and inhibition tests. Tapping and balance showed a similar trend, but no statistically significant difference in performance. Conclusion: In sports-related concussions, complex motor tests can be valuable additions in assessing the outcome and recovery. In the current study, using subtasks with varying cognitive demands, it was shown that while simple motor performance was largely unaffected, the more complex tasks induced impaired reaction times for the concussed subjects. The increased reaction times may reflect the disruption of complex and integrative cognitive function in concussions.