Corticospinal tract MRI hyperintensity in X-linked Charcot-Marie-Tooth Disease.

In X-linked hereditary demyelinating neuropathies (CMTX), caused by mutations in Connexin 32, mild subclinical CNS involvement is not unusual. We present a young male patient suffering from genetically proven CMTX who presented with permanent bilateral corticospinal tract hyperintensities in cranial MRI -- a finding previously described to be characteristic for amyotrophic lateral sclerosis. MRI seems to be able to visualize corticospinal tract abnormalities, even if subclinical, in CMTX.

MR-pathologic comparison of the upper spinal cord in different motor neuron diseases.

This MRI study was performed to evaluate in vivo alterations of the spinal cord in defined subgroups of motor neuron diseases. Standard MRI examinations of the cervical and thoracic spinal cord in sporadic amyotrophic lateral sclerosis (ALS; n = 39), sporadic lower motor neuron disease (LMND; n = 19), Kennedy's disease (KD; n = 19) and a control group (n = 96) were analyzed with respect to spinal cord signal changes and the thickness of the spinal cord. No significant changes in thickness or signal alterations were observed when comparing ALS, LMND and control groups with one another. However, in KD patients significant upper spinal cord atrophy was detected at the cervical level as compared with all other groups. At the thoracic level, KD patients had significant upper cord atrophy as compared with controls and LMND. Marked atrophy of the upper spinal cord seems to be a feature of the KD-associated central-peripheral distal axonopathy.

Alike performance during nonverbal episodic learning from diversely imprinted neural networks.

Performance on neuropsychological testing permits inferences to be made regarding neural networks required to solve the task. In healthy young human subjects it is common sense that differential performance in cognitive tasks results from recruitment of different neural networks and that alike performance results from recruitment of alike neural networks. It was the goal of the present study to investigate whether these assumptions are also valid in cross-cultural studies. To address this, we used functional MRI during a nonverbal episodic memory task with repeated learning of abstract geometric patterns. Behavioural performance in this task was alike over repeated trials in native Chinese and Caucasian subjects. Given this equivalent performance, the distinct pattern of neuronal activation observed is interpreted as the outcome of different culturally imprinted processing routines. In the 'what' and 'where' framework of visuo-spatial processing initial learning in Chinese subjects activated the dorsal stream for analysis of spatial features whereas Caucasians recruited the ventral stream for object identification. With repeated learning Chinese subjects integrated visuo-spatial processing to object coding and vice versa. Thus, imprints of culture result in activation of distinct neural networks and mandate monitoring of both behavioural performance and neural recruitment in cross-cultural studies of cognition.

Aerobic endurance exercise improves executive functions in depressed patients.

BACKGROUND: Aerobic endurance exercise has been shown to improve higher cognitive functions such as executive control in healthy subjects. We tested the hypothesis that a 30-minute individually customized endurance exercise program has the potential to enhance executive functions in patients with major depressive disorder. METHOD: In a randomized within-subject study design, 24 patients with DSM-IV major depressive disorder and 10 healthy control subjects performed 30 minutes of aerobic endurance exercise at 2 different workload levels of 40% and 60% of their predetermined individual 4-mmol/L lactic acid exercise capacity. They were then tested with 4 standardized computerized neuropsychological paradigms measuring executive control functions: the task switch paradigm, flanker task, Stroop task, and GoNogo task. Performance was measured by reaction time. Data were gathered between fall 2000 and spring 2002. RESULTS: While there were no significant exercise-dependent alterations in reaction time in the control group, for depressive patients we observed a significant decrease in mean reaction time for the congruent Stroop task condition at the 60% energy level (p = .016), for the incongruent Stroop task condition at the 40% energy level (p = .02), and for the GoNogo task at both energy levels (40%, p = .025; 60%, p = .048). The exercise procedures had no significant effect on reaction time in the task switch paradigm or the flanker task. CONCLUSION: A single 30-minute aerobic endurance exercise program performed by depressed patients has positive effects on executive control processes that appear to be specifically subserved by the anterior cingulate.

Evidence for quantitative domain dominance for verbal and spatial working memory in frontal and parietal cortex.

Neuroimaging studies in humans have shown that different working memory (WM) tasks recruit a common bilateral fronto-parietal cortical network. Animal studies as well as neuroimaging studies in humans have suggested that this network, in particular the prefrontal cortex, is preferentially recruited when material from different domains (e.g. spatial information or verbal/object information) has to be memorized. Early imaging studies have suggested qualitative dissociations in the prefrontal cortex for spatial and object/verbal WM, either in a left-right or a ventral-dorsal dimension. However, results from different studies are inconsistent. Moreover, recent fMRI studies have failed to find evidence for domain dependent dissociations of WM-related activity in prefrontal cortex. Here we present evidence from two independent fMRI studies using physically identical stimuli in a verbal and spatial WM task showing that domain dominance for WM does indeed exist, although only in the form of quantitative differences in activation and not in the form of a dissociation with different prefrontal regions showing mutually exclusive activation in different domains. Our results support a mixed dimension model of domain dominance for WM within the prefrontal cortex, with left ventral prefrontal cortex (PFC) supporting preferentially verbal WM and right dorsal PFC supporting preferentially spatial WM. The concept of domain dominance is discussed in the light of recent theories of prefrontal cortex function.