The role of the human thalamus in language and memory: Evidence from electrophysiological studies

Author(s): Ojemann, G. A.

Journal/Book: Brain Cognition. 2000; 42: 525 B St, Ste 1900, San Diego, CA 92101-4495, USA. Academic Press Inc. 218-230.

Abstract: The data reviewed hc re indicate that electrical stimulation of the dominant ventrolateral thalamus can produce deficits in language processing th;lt are not seen after similar stimulation of the nondominant ventrolateral thalamus. The nature of the language deficit produced varies, depending upon the rostrocaudal location of the stimulation site. Stimulation of the anterior left ventrolateral thalamus in right-handed patients resulted in production of a repeated erroneous word, stimulation of the medial ventrolateral thalamus evoked perseveration, and stimulation of the posterior ventrolateral thalmus and anterior pulvinar resulted in misnaming and omissions. Additional studies have examined the effect of electrical thalamic stimulation on verbal and nonverbal short-term memory. Left (but not right) ventrolateral thalamic stimulation during verbal memory input greatly decreased subsequent recall errors. While stimulation during verb:ll memory retrieval increased recall errors. This finding contrasted with those obtained from studies on nonverbal memory, in which right ventrolateral stimulation during memory input decreased recall errors, while left thalamic stimulation at the same stage increased recall errors. Left pulvinar stimulation disrupted verbal memory processing, while right pulvinar stimulation disrupted nonverbal memory processing. Limited evidence suggests that the effects of thalamic electrical stimulation on verbal memory may persist for several days after the stimulation has ended. The lateralization of thalamic functions also affects the motoric aspects of speech production. Left (hut nor right) ventrolateral thalmic stimulation disrupted speech articulation and increased the expiratory phase of respiration. The fact that these motor effects were evoked from the same general area of the thalamus that produced the language deficits discussed above mises the possibility that the thalamus is involved in coordinating the cognitive and motoric aspects of language production. A model of thalamic function is discussed in which defined regions of the thalamus operate as a ''specific alerting response,'' increasing the input to memory of category-specific material while simultaneously inhibiting retrieval from memory.

Note: Article Ojemann GA, Univ Washington, Dept Neurol Surg, 1959 NE Pacific St, Box 356470, Seattle,WA 98195 USA

Keyword(s): ELECTRICAL-STIMULATION; HUMAN-BRAIN; CORTEX; SPEECH

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