Contributions of the left intralaminar and medial thalamic nuclei to memory. Comparisons and report of a case
M. Mennemeier, E. Fennell, E. Valenstein and K. M. Heilman
Department of Veterans Affairs Medical Center, Gainesville, FL.
A patient complained of memory disturbance after a small left thalamic
infarction. Neuropsychological testing revealed her memory to be normal
provided that she was allowed to rehearse or use semantic encoding
strategies. When these strategies were prevented, her performance was
impaired. Mapping of the lesion demonstrated involvement of the caudal
intralaminar nuclei (centre median and parafascicular nuclei), and portions
of the medial nuclei (medioventral [reuniens], centromedial, and the most
inferior aspect of the mediodorsal nucleus). The majority of mediodorsal
nucleus, the mammillary bodies, the mammillothalamic tract, and the
anterior thalamic nuclei, were spared. A comparison among our patient's
performances and those of alcoholic Korsakoff patients, patient NA, and
amnestic patients with circumscribed diencephalic lesions suggests that
there are two distinct behavioral and anatomic types of memory impairment
associated with diencephalic lesions. The severe amnesia associated with
damage to the mammillary bodies, midline nuclei, mammillothalamic tract,
and/or dorsomedial nucleus of the thalamus (eg, Korsakoff and NA) is
characterized by encoding deficits that never approximate normal
performance. The memory disturbance associated with damage to the
intralaminar and medial nuclei of the thalamus is milder and is
characterized by severe distractibility.
