Nicole von Steinbüchel

Cortical involvement in temporal reproduction: evidence for differential roles of the hemispheres.

Only few studies have addressed temporal processing for durations longer than 1 s, and even fewer studies have investigated cortical involvement in time perception, in particular temporal production and reproduction. The present study investigated temporal reproduction in healthy control subjects and patients with anterior or posterior cortical lesions in the left or right hemisphere, or with subcortical left-hemispheric lesions. The paradigm involved presentation of either auditory or visual stimuli of 10 different standard intervals ranging from 1 to 5.5 seconds duration. Participants were required to reproduce the duration of a stimulus. Our results show that: (1) temporal reproduction across this temporal range can be better described with two separate linear regressions (bilinear approach) than with one single linear regression, thus contrasting the scalar timing concept; (2) that patients can, regardless of the hemisphere lesioned, perform reproductions of durations smaller than 2-3 s with reasonable accuracy; and (3) that patients with right-hemispheric lesions appear to be impaired in reproductions of stimuli longer than 2-3 s. Since attention appeared not to be impaired in the patients tested, the findings suggest that the integrity of the right hemisphere seems to be critical for temporal reproduction of intervals longer than 2-3 s.

Quality of Life after Brain Injury (QOLIBRI): Scale Validity and Correlates of Quality of Life

The QOLIBRI (Quality of Life after Brain Injury) is a novel health-related quality-of-life (HRQoL) instrument specifically developed for traumatic brain injury (TBI). It provides a profile of HRQoL in six domains together with an overall score. Scale validity and factors associated with HRQoL were investigated in a multi-center international study. A total of 795 adults with brain injury were studied from 3 months to 15 years post-injury. The majority of participants (58%) had severe injuries as assessed by 24-h worst Glasgow Coma Scale (GCS) score. Systematic relationships were observed between the QOLIBRI and the Glasgow Outcome Scale-Extended (GOSE), Hospital Anxiety and Depression Scale (HADS), and SF-36. Within each scale patients with disability reported having low HRQoL in two to three times as many areas as those who had made a good recovery. The main correlates of the total QOLIBRI score were emotional state (HADS depression and anxiety), functional status (amount of help needed and outcome on the GOSE), and comorbid health conditions. Together these five variables accounted for 58% of the variance in total QOLIBRI scores. The QOLIBRI is the first tool developed to assess disease-specific HRQoL in brain injury, and it contains novel information not given by other currently available assessments.

DAILY RHYTHM OF TEMPORAL RESOLUTION IN THE AUDITORY SYSTEM

Over a period of 24 hours, fusion thresholds (click durations 100 micros) were assessed in 7 subjects. Over the same period, order thresholds (click duration of 1 ms) were measured in 10 subjects (12 independent sessions). Auditory fusion thresholds showed a diurnal rhythm with a maximum performance (shortest intervals) around midnight. In contrast, order thresholds appear to be independent on the time of day. Sex specific differences in threshold levels were only observed in order thresholds but not in fusion thresholds.

Auditory temporal-order judgement is impaired in patients with cortical lesions in posterior regions of the left hemisphere.

Auditory temporal-order judgement was investigated in patients suffering from unilateral focal brain lesions, localized in anterior or posterior regions of the left hemisphere (LH) (resulting in non-fluent or fluent aphasia, respectively), or in predominantly subcortical regions of this hemisphere (without aphasic syndromes) and in anterior or posterior regions of the right hemisphere. The temporal order threshold was measured as the minimum time interval between two clicks presented consecutively and binaurally via headphones (one to each ear) that was necessary for a subject to indicate the temporal order of the two stimuli. Only the patient group with fluent aphasia showed a significantly increased mean temporal-order threshold as compared to the controls. Our results indicate that fine temporal resolution for auditory stimuli is predominantly associated with posterior regions of the LH.

Electronic measurement of adherence to pediatric antiretroviral therapy in South Africa.

Background: Little is known about adherence to pediatric antiretroviral regimens in countries of the developing world. Both assessment methods and predictors of adherence need to be examined to deliver appropriate health care to the growing patient population in resource-limited settings. Methods: We conducted a prospective study of adherence in a pediatric HIV outpatient clinic in Cape Town, South Africa. Adherence was assessed by the Medication Event Monitoring System (MEMS) and caregiver self-report by Visual Analogue Scale (VAS). Virologic response was recorded at study baseline and closest follow-up visit, child and caregiver data were collected by questionnaires. Results: For 73 children followed, median adherence by MEMS was 87.5%; median caregiver reported adherence was 100%. MEMS and caregiver report differed in reporting excellent (>95%) adherence, with MEMS classifying 36% of subjects in this category, whereas caregiver report classified 91%. Overall, 65% of children achieved virologic suppression after the study period. MEMS adherence was significantly associated with virologic suppression. The highest specificity was obtained when adjusting the data for doses taken at the prescribed time (91.3%). No predictors for the differences between MEMS and caregiver reported adherence could be identified. Conclusions: Adherence to pediatric antiretroviral regimens in South Africa is not lower than in the developed world, yet not high enough to guarantee long-term treatment success. Caregiver report seems unreliable in this setting. MEMS is a feasible and accurate measure of adherence for children on liquid drug formulations.

Temporal processing disorders in patients with Broca's aphasia

We report an association between a language deficit following brain lesion and a new strategy in temporal integration. Patients with different brain lesions mentally grouped sequences of identical acoustic stimuli generated at various frequencies. They were asked while listening to the stimuli to accentuate every second, third or other stimulus to create an individual rhythmic pattern. After each sequence patients reported how many stimuli they had united into a perceptual unit. The integration interval was defined as the number of reported stimuli multiplied by the temporal interval between two successive stimuli. Results indicate different integration strategies depending on the lesion site, i.e. Brocas aphasics behaving differently than all other patient groups. At lower frequencies they showed longer, at higher frequencies they displayed shorter integration. From this observation we conclude that the Brocas patients acquired a new strategy because of the lesion; they relied on mental counting and less on automatic temporal integration, which is usually the case.

Hemispheric specialisation for self-paced motor sequences

Temporal aspects of motor control were investigated in patients with infarction to the brain with two finger-tapping tests. In the self-paced tapping task patients with cortical left-hemispheric lesions were slowed down and patients with left-hemispheric subcortical injuries were consistently faster as compared with control subjects and patients with right hemispheric cortical lesions. The results point to the dominant control of the left-hemisphere in voluntarily timed action and to a special time range of 250-300 ms involved in motor behaviour.

Timing in perceptual and motor tasks after disturbances of the brain

Abstract For an understanding of how functions are represented in the brain it appears useful to distinguish between content-related or complex functions, e.g. perception, learning, memory and action, and logistics-related or elementary functions, namely activation and temporal integration and organisation. Elementary functions that temporally structure the content-related functions are a necessary prerequisite of conscious experience and actions. With various experimental paradigms different levels of temporal processing and organisation of information and behaviour are assessed, which can be differentially impaired depending on the nature and localization of damage to the brain. This will be shown for patients with focal brain lesions, for patients with symptomatic HIV infection and for patients with epilepsy who received different treatment.

Self-awareness and health-related quality of life after traumatic brain injury

Objective:To investigate the relations among self-awareness (SA), impaired SA, and health-related quality of life (HRQOL) after traumatic brain injury (TBI). Participants:One hundred forty-one adults hospitalized with TBI and their significant others from a cross-sectional multicenter study. Using Glasgow Coma Scale classification, 32 participants had severe injuries, 29 moderate, 44 mild, and 25 complicated mild TBI. Measures:Patient Competency Rating Scale for Neurorehabilitation; Short Form-36 Health Survey; Cognitive Quality of Life; Quality Of Life after Brain Injury; Hospital Anxiety and Depression Scale; Profile of Mood States; Glasgow Outcome Scale Extended. Method:Patient Competency Rating Scale for Neurorehabilitation ratings made by participants and their significant others were used to assess SA and discrepancies between the 2 ratings were used to define impaired SA. Results:Significant associations were identified between SA and HRQOL, anxiety, depression, and severity of injury. Participants with and without impaired SA differed in cognitive HRQOL and leisure activities. Using multiple regression, no direct predictors of SA were identified, although interaction effects were observed. Conclusion:After TBI, lower SA is associated with higher estimates of HRQOL, particularly in the cognitive domain. Although the associations are modest, the assessment of SA should play a role in the interpretation of reported HRQOL after TBI.

Temporal ranges of central nervous processing: clinical evidence

Abstract The organization of the time frames for perceiving, generating, and updating information in the CNS has as of yet received little attention despite its elementary character for human behavior. We investigated temporal epochs in perceiving, acting, and updating in patients with anterior and posterior lesions of the left and right hemisphere, in patients with lesions in the left hemisphere without aphasia, and in healthy controls. Three temporal ranges, 30, 300, and 3000 ms, were assessed with different psychophysical paradigms. Prolongation of the temporal perception of order (30 ms) was most pronounced with left posterior lesions, of repetitive action (300 ms) with left anterior lesions, and updating (3000 ms) with left and right anterior lesions. Temporal deficits are group as well as parameter specific. Our results support the notion of coordinated coexistence of different temporal mechanisms.