Sensory-motor cortex reorganization in Alzheimer's disease: an MEG study

Objectives: Aim of our study was to evaluate possible signs of the high capability of the sensori-motor cortex to reorganize the neural circuitry that is being affected by the disease in nearby areas less affected by degeneration. Methods: We studied 16 AD patients and 16 controls by recording from sensorimotor brain areas their magnetoencephalographic (MEG) fields at rest and during contralateral median nerve stimulation. Latency of activation and position of the marker of primary somatosensory area devoted to hand control were estimated, in addition to spectral properties of these regions oscillatory activity at rest. Results: An unambiguous spatial shift of the patients' sensori-motor generators, with no change in their latencies or strength. Interestingly, this reorganization appeared more evident in patients with less severe clinical condition (mini-mental state examination, MMSE, in the 20 25 range), regressing below significant difference from controls with worsened clinical state (MMSE = 7 20). Low-band activity (delta and theta bands) increased in patients with a linear behaviour. Conclusion: More evident signs of cerebral plasticity in AD patients with less severe clinical damage may suggest that the capability of sensorimotor regions to reorganize can contribute to the well known resistance of sensorimotor