Taking both sides: do unilateral anterior temporal lobe lesions disrupt semantic memory?

Abstract

The most selective disorder of central conceptual knowledge arises in semantic dementia, a degenerative condition associated with bilateral atrophy of the inferior and polar regions of the temporal lobes. Likewise, semantic impairment in both herpes simplex virus encephalitis and Alzheimer's disease is typically associated with bilateral, anterior temporal pathology. These findings suggest that conceptual representations are supported via an interconnected, bilateral, anterior temporal network and that it may take damage to both sides to produce an unequivocal deficit of central semantic memory. We tested and supported this hypothesis by investigating a case series of 20 patients with unilateral temporal damage (following vascular accident or resection for tumour or epilepsy), utilizing a test battery that is sensitive to semantic impairment in semantic dementia. Only 1/20 of the cases, with a unilateral left lesion, exhibited even a mild impairment on the receptive semantic measures. On the expressive semantic tests of naming and fluency, average performance was worse in the left- than right-unilateral cases, but even in this domain, only one left-lesion case had scores consistently more than two standard deviations below control means. These results fit with recent parallel explorations of semantic function using repetitive transcranial magnetic stimulation as well as functional imaging in stroke aphasic and neurologically intact participants. The evidence suggests that both left and right anterior temporal lobe regions contribute to the representation of semantic memory and together may form a relatively damage-resistant, robust system for this critical aspect of higher cognition.

The neural network associated with lexical-semantic knowledge about social groups

“…On the other hand, LGG patients' deficits, although milder than HGG patients', are more pronounced immediately after surgical resection (Campanella et al, 2015), and some specific lesion locations tend to compensate minimally (Ius, Angelini, Thiebaut de Schotten, Madonnet & Duffau, 2011). Moreover, previous studies testing semantic memory in patients with unilateral lesions (Campanella, D'Agostini Skrap & Shallice,2010, Lambon Ralph et al, 2010 or bilateral lesions but more pronounced within one hemisphere (Lambon Ralph et al, 2001), reported prominent verbal output deficits and mild or normal receptive performance. In a computation model proposed to account for this phenomenon (Lambon Ralph et al, 2001), semantic knowledge is hypothesised to rely on a bilateral, distributed semantic system, with the left hemisphere semantic areas having privileged connections to the left-M A N U S C R I P T…”

“…Patients with unilateral brain damage have been reported with impaired performance on tasks involving verbal production as in picture naming, but spared recognition abilities (Lambon Ralph, Cipolotti, Manes & Patterson, 2010;Lambon Ralph, Ehsan, Baker, & Rogers 2012;Drane et al, 2008). Moreover, patients with semantic dementia tend to show different types of impairment depending on the predominant laterality of the atrophy, with patients with more pronounced left atrophy showing disproportionate production impairment compared to comprehension, and patients with a more pronounced right atrophy showing a similar impairment in production and comprehension (Lambon Ralph, McClelland, Patterson, Galton & Hodges, 2001).…”

Imagining future events in patients with unilateral temporal lobe epilepsy

“…Two of these three studies (Viskontas et al, 2000;Voltzenlogel et al, 2006) considered the score obtained on the personal semantic section of the AMI, and the remaining study employed the external composite score (which includes not only semantic details, but also repetitions and other types of details) of the Autobiographical Interview (AI; Levine, Svoboda, Hay, Winocur, & Moscovitch, 2002) as a measure of 'semantic' memory. A study that examined the impact of unilateral temporal lobe damage on semantic memory in general showed that on expressive semantic tasks (i.e., naming, fluency), patients with left unilateral lesions obtained significantly lower scores relative to patients with right unilateral lesions (Ralph, Cipolotti, Manes, & Patterson, 2010). The between-group difference, however, was not significant on receptive semantic measures.…”

Receptive vocabulary and semantic knowledge in children with SLI and children with Down syndrome

“…Contemporary research evidence about the location and organisation of semantic memory largely comes from studying adult neuropsychology patients, particularly those with semantic dementia (SD) who present with progressive loss of conceptual knowledge (e.g., Bozeat, Lambon Ralph, Patterson, Garrard, & Hodges, 2000;Lambon Ralph, Cipolotti, Manes, & Patterson, 2010;Lambon Ralph & Howard, 2000). This research suggests that semantic memory is represented bilaterally in anterior temporal lobe regions (Lambon Ralph, Sage, Jones, & Mayberry, 2010;Pobric, Jefferies, & Lambon Ralph, 2007).…”