Visual short-term store can compensate for a defective phonological short-term store in patients with apraxia of speech

Neuropsychology. 2013 Nov;27(6):628-41. doi: 10.1037/a0034033. Epub 2013 Sep 16.

Abstract

Objective: The aim of the study was to investigate whether, within the phonological short-term memory (STM) system, speech articulation disorders primarily due to cortical damage are associated with deficits in the phonological recoding of visual-verbal material, and whether the visual short-term store (STS) can compensate for inefficient access to the phonological STS, as suggested in previous reports.

Method: Two patients (AE and TM) with apraxia of speech due to atrophic cerebral damage were administered a battery of tasks devised to explore the organization of the phonological STM.

Results: AE's span was normal and TM's span was markedly reduced. Phonological similarity and word-length effects: Both patients showed the effects in visual presentation; the effect was less evident in verbal presentation. This suggests a phonological STS disorder and preserved rehearsal/phonological recoding, consistently with involvement of the left parietal regions, which was documented by the MRI in both patients. Unexpectedly, TM had a longer span for similar than for dissimilar words in visually presented stimuli. Silent phonology (on written material): At variance with controls, stress assignment improved during unattended speech both in AE and TM, while in both patients and controls a detrimental effect of unattended speech was documented in the initial sound task.

Conclusions: To account for this unusual pattern of results, we hypothesized that whenever possible, AE and TM adopt the strategy that takes advantage of the visual STM store to compensate for a defective phonological STS.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Apraxias / complications*
  • Apraxias / etiology
  • Atrophy / complications
  • Atrophy / pathology
  • Cerebrum / pathology
  • Female
  • Humans
  • Linguistics
  • Magnetic Resonance Imaging
  • Male
  • Memory Disorders / diagnosis
  • Memory Disorders / etiology*
  • Memory, Short-Term / physiology*
  • Neuropsychological Tests
  • Speech*
  • Verbal Learning / physiology