Elsevier

Brain and Cognition

Volume 50, Issue 2, November 2002, Pages 178-193
Brain and Cognition

Patterns of impaired verbal, spatial, and object working memory after thalamic lesions

https://doi.org/10.1016/S0278-2626(02)00502-XGet rights and content

Abstract

Working memory processes in six individuals with isolated thalamic lesions were assessed. Participants were given a verbal, spatial, and object n-back task, each at three levels of task load (1-back, 2-back, and 3-back). Relative to a control group, the patients were impaired on the verbal and spatial n-back tasks, and possibly on the object n-back task as well. None of the patients showed impaired short-term memory as measured by digit span. Group differences on trials measuring matching, sequencing, and inhibitory abilities were consistent with other reports suggesting that thalamic lesions may impair the operation of executive processes.

Section snippets

The present study

Investigations of the contributions of the thalamus to working memory have been very limited. The present study pursues several questions about the possible role of the thalamus. First, does thalamic damage affect only verbal working memory or does it also affect spatial and object working memory? In order to address this question, the present study had thalamic patients perform three versions of an n-back task: a verbal task requiring matching responses of letter stimuli, a spatial task

Participants

Six patients with thalamic infarction were recruited through the Wake Forest University School of Medicine. Patients were chosen based upon the criteria that their brain lesion was restricted to the thalamus as identified by MRI scans analyzed by the third author, and that the patient was free from any major illnesses or medication use thought to affect cognitive performance. The areas of patients’ thalamic lesions are presented in Table 1. Five of the patients had lesions located in the right

Results

Patient performance was evaluated by treating all six patients as a group and comparing their performance to the control group means. ANOVA and t tests were conducted to detect overall differences between the two groups in the digit span tasks and at several levels of the working memory tasks.

Discussion

The clearest findings in this study were the group differences on the verbal working memory measure. The accuracy scores of the patient group were equivalent to the control group at the 1-back level but then diverged at the higher task load levels (2-back and 3-back) as patients’ accuracy scores dropped. Patient impairments on the verbal task produced a pattern that is consistent with both neuroimaging reports of thalamic activation and previous findings from case studies. Equal patient and

Is the thalamus involved exclusively in verbal working memory or does it also function in spatial and object working memory?

Findings of thalamic activation during working memory tasks in functional neuroimaging studies have so far only resulted from performance of a verbal n-back task and only at the higher task loads (Awh, Smith, & Jonides, 1995; Callicott et al., 1999; Jonides et al., 1997). Although one study conducted with a spatial version of the n-back task did not find significant thalamic activation, the additional systems of the visuospatial sketchpad that are a part of Baddeley’s working memory model (1998)

What working memory process does thalamic damage affect?

Consistent with previous case studies of thalamic patients, all six of the patients in the present study had normal spans on the aural and visual forward digit span tasks as well as the digit span task with articulatory suppression. One possible exception is Patient L.B. who had a low-normal score of 5 on the aural digit span. However, this patient also had complaints of hearing problems and discriminating noises since occurrence of her brain damage. This symptom, coupled with the fact that she

Summary

Overall, the present series of thalamic case studies provides further evidence that thalamic damage affects the verbal working memory system and extends those findings to include effects in the spatial and possibly the object working memory systems as well. These data suggest that thalamic lesions do not affect storage or rehearsal processes per se. Group differences on trials measuring matching, sequencing, and inhibitory abilities indicate that the thalamic damage affects the operation of

Acknowledgements

This study was supported in part by a Wake Forest University Cross-Campus Collaborative Research Grant to the second and third authors.

References (41)

  • F Attneave et al.

    The quantitative study of shape and pattern perception

    Psychological Bulletin

    (1956)
  • E Awh et al.

    Human rehearsal processes and the frontal lobes: PET evidence

  • A.D Baddeley

    Working memory: Theory and practice

    (1998)
  • A.D Baddeley et al.

    Working memory

  • J.H Callicott et al.

    Physiological characteristics of capacity constraints in working memory as revealed by functional MRI

    Cerebral Cortex

    (1999)
  • B.J Casey

    Disruption of inhibitory control in developmental disorders: A mechanistic model of implicated frontostriatal circuitry

  • S Clarke et al.

    Pure amnesia after unilateral left polar thalamic infarct: topographic and sequential neuropsychological and metabolic (PET) correlations

    Journal of Neurology Neurosurgery and Psychiatry

    (1994)
  • R Cabeza et al.

    Imaging cognition: An empirical review of PET studies with normal subjects

    Journal of Cognitive Neuroscience

    (2000)
  • A.R Damasio

    On some functions of the human prefrontal cortex

  • D Dagenbach et al.

    Human verbal working memory impairments associated with thalamic damage

    International Journal of Neuroscience

    (2001)

    • Cited by (0)

    1

    Department of Neurology, WFUBMC, USA; Cingulum Neurosciences Insititute, Inc., USA; Absher Neurology, PA, USA.

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