^BBSnline

Episodic memory, amnesia, and the hippocampal-anterior thalamic axis

Aggleton, John P. and Brown, Malcolm W. (1999) Episodic memory, amnesia, and the hippocampal-anterior thalamic axis.

Short Abstract:

Using new information from both clinical and experimental (lesion, electrophysiological, and gene-activation) studies with animals, the anatomy underlying anterograde amnesia is reformulated. The distinction between temporal lobe and diencephalic amnesia is of limited value because a common feature of anterograde amnesia is damage to part of an "extended hippocampal system" comprising the hippocampus, the fornix, the mamillary bodies and the anterior thalamic nuclei.

Long Abstract:

Using new information from both clinical and experimental (lesion, electrophysiological, and gene-activation) studies with animals, the anatomy underlying anterograde amnesia is reformulated. The distinction between temporal lobe and diencephalic amnesia is of limited value because a common feature of anterograde amnesia is damage to part of an "extended hippocampal system" comprising the hippocampus, the fornix, the mamillary bodies and the anterior thalamic nuclei. This view, which can be traced back to Delay and Brion (1969), differs from other recent models in placing critical importance on the efferents from the hippocampus via the fornix to the diencephalon. These are necessary for the encoding and, hence, the effective subsequent recall of episodic memory. An additional feature of this hippocampal - anterior thalamic axis is the presence of projections back from the diencephalon to the temporal cortex and hippocampus that also support episodic memory. In contrast, this hippocampal system is not required for tests of item recognition that primarily tax familiarity judgements. Familiarity judgements reflect an independent process that depends on a distinct system involving the perirhinal cortex of the temporal lobe and the medial dorsal nucleus of the thalamus. In the large majority of amnesic cases both the hippocampal - anterior thalamic and the perirhinal - medial dorsal thalamic systems are compromised, leading to severe deficits in both recall and recognition.

Keywords:	amnesia, memory, hippocampus, fornix, thalamus, temporal cortex
Subjects:	Neuroscience: Behavioral Neuroscience Biology: Behavioral Biology Psychology: Cognitive Psychology Psychology: Learning and Memory Neuroscience: Neuroanatomy Neuroscience: Neurophysiology Neuroscience: Neuropsychology Psychology: Physiological Psychology Psychology: Psychobiology
ID code:	bbs00000420
Deposited by:	John P Aggleton on 30 April 2001