Chilvers, R.J.; (2008) A story without words: investigation of a dominantly inherited verbal memory disorder in a large family. Doctoral thesis , UCL (University College London).

Abstract

To date, there have almost no examples of families where a specific cognitive deficit is inherited with the preservation of closely allied cognitive systems. This thesis describes a series of investigations to define and characterise the phenotype of a large family (the JR family) with an apparently dominantly inherited disorder of verbal memory spanning four living generations. Initial neuropsychological assessment of affected family members revealed a pattern of preserved intelligence with superior nonverbal to verbal IQ. Impaired verbal knowledge, particularly vocabulary was seen. Verbal recall memory was significantly impaired but visual recall was intact. Discrepancies in IQ or memory abilities were not found in family members without the memory problem. Further investigations showed that the verbal memory deficit could not be explained by an underlying language disorder. Affected JR family members did not have generalised deficits in language processing or phonological short-term memory. However they did show deficits in subtests that placed high demands upon verbal memory, and those requiring the retention of semantic information. Evidence was then sought to test the hypothesis that pictorial support during encoding would improve prose recall. This was found to be the case, with pictures that were most semantically relevant being of most benefit. There was clearly a possibility, on the basis of preliminary findings, that the verbal memory deficit could be the result of lexical-semantic impairments in short-term memory. Typical lexical-semantic effects were seen in affected family member’s performance on word span tasks, but not sentence repetition tasks. Recall of sentences that required the retention of a high semantic load showed the greatest deficit compared to unrelated controls. Finally, a further set of experiments sought to establish whether affected JR cases had an underlying semantic processing deficit. This was not found, but a specific impairment in word knowledge, particularly abstract word knowledge was revealed. The results of these studies are interpreted using structural and processing models of memory. Conclusions indicate, provisionally, that the verbal memory deficit seen in affected JR cases is the consequence of an impaired binding mechanism between phonological and semantic representations at the interface of short-term and long-term memory.

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