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Biomedical subjects

H Johansen-Berg

Publications and source records attributed to H Johansen-Berg.

At least 19 recordsLinked to original sources
PubMed2002

In Briefs.

Explore the source record for details and available documents.

Journal Article↗
PubMed2002

An expanded cortical representation for hand movement after peripheral motor denervation.

OBJECTIVES: Functional reorganisation of the motor or sensory cortex has been demonstrated in animals after section of mixed peripheral nerves. Here functional changes in the motor cortex specifically after peripheral motor denervation in humans are investigated. METHODS: Functional MRI (fMRI) was used to study brain activation during a finger flexion-extension task in patients with a late onset, acquired pure motor neuropathy (n=6), contrasting results with those from patients with pure sensory neuropathies (n=4) or healthy controls (n=7). RESULTS: Increases in the extent of activation in the motor cortex both ipsilateral and contralateral to the hand moved were found in the patients with motor neuropathy. The neuroanatomical localisation of the mixed contralateral sensorimotor cortex activation volume was more posterior for the patients with motor neuropathy than for the healthy controls (mean difference, 12 mm, p<0.05). The pure sensory neuropathy group by contrast showed no change in the extent of activation relative to healthy controls and a trend for more anterior primary sensorimotor cortex activation (p<0.06). To test whether the increased activation volumes found in patients with motor neuropathy were a result simply of factors such as increased effort with movement rather than the motor denervation, patients with hand weakness from inclusion body myositis (n=4) were studied while making similar hand movements. No differences in either the numbers of significantly activated voxels or in their localisation were found relative to healthy controls (n=10). CONCLUSIONS: These results provide a novel demonstration that peripheral denervation (as distinguished from factors related to weakness) leads to functional reorganisation of the sensorimotor cortex in the adult brain. This suggests that adaptive responses to motor denervation involve the central as well as the peripheral nervous system.

Adult↗
PubMed2002

Altered hemodynamic responses in patients after subcortical stroke measured by functional MRI.

BACKGROUND AND PURPOSE: Blood oxygenation level-dependent (BOLD) functional MRI (fMRI) is a promising method for defining brain recovery after stroke quantitatively. Applications thus far have assumed that the BOLD hemodynamic response in patients after stroke is identical to that in healthy controls. However, because of local vascular compromise or more diffuse vascular disease predisposing to infarction, this assumption may not be justified after stroke. We sought to test whether patients who have suffered a lacunar stroke show BOLD fMRI response characteristics identical to those of healthy controls. METHODS: We measured the BOLD fMRI signal time course in the sensorimotor cortex contralateral to the affected hand with finger- or hand-tapping tasks for minimally or mildly impaired right-handed patients (n=12) after lacunar strokes causing limb weakness and for healthy controls (n=20). RESULTS: With a right-handed sequential finger-tapping task, the rate of rise and maximum increase of the BOLD signal in the contralateral sensorimotor cortex were > 30% lower (P< or =0.01) in the stroke patients. Similar relative decreases were found for the same task performed with the left hand. These changes were found in patients both in the hemisphere affected by stroke and in the unaffected hemisphere, suggesting that the BOLD fMRI time course differences observed arise from a diffuse functional pathology. The difference between patients and controls is not a result of age alone, since differences were not found between the younger (n=10; aged 22 to 38 years) and the older (n=10; aged 56 to 83 years) healthy controls. The effect also does not seem to be dependent on the specific hand movement task used. CONCLUSIONS: The magnitude of the BOLD fMRI response can be reduced in stroke patients even if infarcts do not involve the cortex. This may be a consequence of the stroke, but the observation that the BOLD signal time course is similar in the affected and unaffected hemispheres suggests that it also could result from preexisting pathophysiological changes in the cerebral microvasculature.

Adult↗
PubMed2001

Cognitive neuroscience: early learning centres.

Learning leads to neural changes often considered to be driven by 'smart' areas of the brain. A recent study of the cellular changes that underlie perceptual learning has found that plasticity in the primary visual cortex V1 is necessary for learning and the changes that correlate with learning are more complex than one might expect.

Animals↗
PubMed2001

Counter-stimulatory effects on pain perception and processing are significantly altered by attention: an fMRI study.

Counter-stimulation reduces pain perception; however, the role of attention during this process is rarely discussed despite attention itself being a well known modulator of pain perception. This study investigated the effect of attentional modulation on pain perception during counter-stimulation using fMRI. Subjects received a noxious thermal stimulus together with an innocuous vibratory counter-stimulus. Subjects directed their attention towards either pain, vibration, or a neutral visual stimulus. During painful and counter-stimulation all subjects reported a reduction in pain perception when attending to counter-stimulation compared with attending to pain. Imaging data supported this behavioural finding showing reduced activity in pain processing areas (anterior cingulate, insula, thalamus). These results suggest attention plays an important part in the pain relief experienced from counter-stimulation.

Adult↗