Abstract
This study seeks to confirm whether lesions in posterior regions of the brain involved in visuo-spatial processing are of functional relevance to the processing of words with spatial meaning. We investigated whether patients with Posterior Cortical Atrophy (PCA), an atypical form of Alzheimer’s Disease which predominantly affects parieto-occipital brain regions, is associated with deficits in working memory for spatial prepositions. Case series of patients with PCA and matched healthy controls performed tests of immediate and delayed serial recall on words from three lexico-semantic word categories: number words (twelve), spatial prepositions (behind) and function words (e.g., shall). The three word categories were closely matched for a number of psycholinguistic and semantic variables including length, bi-/tri-gram frequency, word frequency, valence and arousal. Relative to controls, memory performance of PCA patients on short word lists was significantly impaired on spatial prepositions in the delayed serial recall task. These results suggest that lesions in posterior parieto-occipital regions specifically impair the processing of spatial prepositions. Our findings point to a pertinent role of posterior cortical regions in the semantic processing of words with spatial meaning and provide strong support for modality-specific semantic theories that recognize the necessary contributions of sensorimotor regions to conceptual semantic processing.
Highlights
Understanding how words and their meanings are represented and processed in the human brain has been a central topic in cognitive neuroscience
In immediate serial recall (ISR), Posterior Cortical Atrophy (PCA) patients made an average of 24.7 errors (SD = 13.4, 34.3% errors) while control subjects made an average of 17.5 errors (SD = 8.2, 24.3% errors)
In delayed serial recall (DSR), PCA cases made an average of 31 errors (SD = 10.1, 43% errors) while controls made an average of 19.8 errors (SD = 7.9, 27.5% errors)
Summary
Understanding how words and their meanings are represented and processed in the human brain has been a central topic in cognitive neuroscience. Impaired Preposition Processing in PCA pertaining to colours engage temporal regions of the brain (Martin et al, 1995; Pulvermüller and Hauk, 2006; Simmons et al, 2007) and words denoting spatial relations (i.e., spatial prepositions) activate left inferior parietal regions (Damasio et al, 2001; Noordzij et al, 2008) These differential activations in sensory and motor brain regions suggest the involvement of action and perception systems in the processing of different semantic word categories. Shebani and Pulvermüller (2018) have shown that performing movements with the hands and feet has a causal influence on the processing of action words by differentially impairing or enhancing working memory for arm- and leg-related action words depending on movement type These studies demonstrate the functional relevance of sensorimotor systems to semantic processing
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