AI Article Synopsis
- The study investigates cerebral blood flow changes in patients with localized thalamic lesions to better understand cortical activation mechanisms.
- Patients with specific thalamic lesions showed reduced blood flow in the primary sensorimotor cortex at rest, correlating with sensory deficits, but still demonstrated normal activation during hand vibration.
- These findings suggest that cortical activation mechanisms are complex, highlighting the need for careful interpretation of activation patterns in patients with brain lesions, even if they show no apparent deficits.
Article Abstract
Background And Purpose: We know remarkably little about the mechanisms underlying cortical activation. Such mechanisms might be better understood by studying the effect of well-localized lesions on the cortical activations in simple paradigms.
Methods: We used H(2)(15)O and positron emission tomography to measure regional cerebral blood flow (rCBF) at rest and during hand vibration in 7 patients with unilateral thalamic lesion involving the ventroposterior (VP) somatosensory thalamic relay nuclei. We compared the results with those obtained in 6 patients with thalamic lesions sparing the VP nuclei and 6 healthy controls.
Results: The patients with VP lesions had a selective hypoperfusion at rest in the ipsilesional primary sensorimotor cortex (SM1). This hypoperfusion was significantly correlated with the degree of contralateral somatosensory deficit. This abnormality may reflect the deafferentation of SM1 from its somatosensory thalamic input. Despite this deafferentation, the ipsilesional SM1 was normally activated by the vibration of the hypoesthetic hand.
Conclusions: The fact that a lesion of the somatosensory thalamic relay nuclei alters the rCBF at rest in SM1 but not its activation by hand vibration indicates that the mechanism of cortical activation is complex, even in the case of simple sensory stimulation. In addition, a dissociation may occur between obvious neurological deficits and apparently normal activation patterns, which suggests that activation studies should be interpreted cautiously in patients with focal brain lesions.
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| http://dx.doi.org/10.1161/01.str.30.12.2651 | DOI Listing |
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