Verbal memory in mesial temporal lobe epilepsy: beyond material specificity

Abstract

The idea that verbal and non-verbal forms of memory are segregated in their entirety, and localized to the left and right hippocampi, is arguably the most influential concept in the neuropsychology of temporal lobe epilepsy, forming a cornerstone of pre-surgical decision making, and a frame for interpreting postoperative outcome. This critical review begins by examining some of the unexpressed but inescapable assumptions of the material-specificity model: (i) verbal and non-verbal memory are unitary and internally homogenous constructs; and (ii) left and right memory systems are assumed to be independent, self-contained modules. The next section traces the origins of an alternative view, emanating largely from three challenges to these assumptions: (i) verbal memory is systematically fractionated by left mesial temporal foci; (ii) the resulting components are differentially localized within the left temporal lobe; and (iii) verbal and non-verbal memory functions are not entirely lateralized. It is argued here that the perirhinal cortex is a key node in a more extensive network mediating protosemantic associative memory. Impairment of this fundamental memory system is a proximal neurocognitive marker of mesial temporal epileptogenesis.

Neuropsychological outcome after epilepsy surgery in patients with bilateral Ammon's horn sclerosis

“…A major reason for this approach is that systematic effects of surgery are mostly found only for verbal memory after left temporal lobe surgery. 42,44,48 However, left and right mesial structures appear to provide highly redundant and compensatory functions in verbal memory processing. 17 Accordingly, it can be observed that nonverbal memory may be sacrificed in favor of verbal memory 20 and that material-specific impairments in TLE are less likely in the presence of generally reduced mental capacities.…”

Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy for Treatment of Drug-Resistant Epilepsy

“…Sparing lateral temporal cortex may preserve connections involved in contextual learning of information based on semantic content and syntactical structure [29]. However, we expect that ablating mesial temporal lobe structures (hippocampus, parahippocampal gyrus) will result in decline in noncontextual memory, such as learning of unrelated series or pairs of words [28,29]. We should note that we have treated patients not yet reported in the literature who did experience verbal memory impairment after SLAH.…”

“…Decline in verbal memory is associated with dominant hemisphere resections [28]. Sparing lateral temporal cortex may preserve connections involved in contextual learning of information based on semantic content and syntactical structure [29]. However, we expect that ablating mesial temporal lobe structures (hippocampus, parahippocampal gyrus) will result in decline in noncontextual memory, such as learning of unrelated series or pairs of words [28,29].…”

Transfer after process-based object-location memory training in healthy older adults.

“…In contrast, the finally included verbal episodic memory tasks primarily required processing of semantically related verbal information. Indeed, associative memory processes seem to contribute little to performance in episodic memory tasks with semantically related verbal information such as texts or word lists (see Saling, 2009), with several studies reporting reduced or even nonexisting performance decrements in older adults for semantically related in comparison to unrelated word pairs (e.g., Badham, Estes, & Maylor, 2012;Naveh-Benjamin, Craik, Guez, & Kreuger, 2005;Patterson, Light, Van Ocker, & Olfman, 2009 Second, because the correct retrieval of object-location associations depends on the retention of both objects and locations in memory (Postma et al, 2008), OLM training practices also memory for objects and memory for locations alongside associative memory.…”