Objective: Thalamic Deep Brain Stimulation (DBS) is reported to be successful in Parkinson patients with motor symptoms resistant to medication as a treatment procedure. Despite evidence of cortico-subcortico-cortical circuit involvement in motor control, the role of this neural circuitry on higher cognitive functions such as language is still controversial. In particular, research evidence pertaining to the impact of ventrolateral thalamic stimulation on linguistic processing is scarce. This paper investigates the effect of right and left thalamus-DBS on memory and language processing in Parkinson patients.

Materials & Methods: In this paper as a case series research we measured memory and language processing in six Parkinson patients (2 left, 2right, 2 bilateral) underwent implantation of deep brain stimulating electrode in ventrolateral thalamic nucleus. The data were collected in two “on” and “off” positions, with at least 40 days time interval in between. The patients were assessed using Wechsler memory test, verbal fluency and some sub-tests of Farsi version of Bilingual Aphasia Test (BAT).

Results: The findings of this research are suggesting an improvement on grammar comprehension and a decline in sentence production and verbal fluency in “on” position versus “off” position, in both groups. The Wechsler memory scores in left thalamus group improved but declined in right thalamus group.

Conclusion: The results indicate that thalamic DBS did not cause any deficit on grammar comprehension and even improved the level of comprehension. On the contrary a decrease in verbal fluency and sentence production, as two high level linguistic processing tasks, was observed. The results confirmed contemporary theories of thalamic participation on language processing and did not confirm a laterality effect on language skills. Although observed difference after thalamic DBS between right and left group on memory score can confirm laterality effect on memory.

Crossed aphasia in dextral (CAD) refers to aphasia occurring after right brain damage in dextral persons. CAD is a rare phenomenon in the world and there has not been any report of crossed aphasia in Persian, that is why we measured to report a Persian patient with crossed aphasia and this is a first report of incidence of CA in Persian. In this case report study, we offered a complete report of a 31-year-oldright handed man with right hemisphere lesion who experienced aphasia after his brain injury. We assessed the patient with Persian version of Bilingual Aphasia Test (BAT), Test of Anomia and Apraxia. In addition, more than 100 utterances of connected speech were gathered and analyzed. According to the results of anomia and apraxia tests, he was at normal level in both of them, but he couldn’t get complete score in BAT, the worst score was achieved in making sentence subtest of BAT. He also had deficits in the syntactic comprehension, grammaticality judgments, lexical decision, verbal fluency and reading comprehension subtests of BAT. Linguistic analysis of his connected speech indicated low speech rate and deficit in using prepositions, compound nouns and verbs. The results confirmed the existence of aphasia and incoherent and non-cohesive speech. The reason of the latter could be deficit in using complex sentences and discourse marker (grammatical problems) and circumlocution, deficit in topic maintenance , using pronoun ambiguouslyand selecting inappropriate words for convey meaning (pragmatic problems related to right hemisphere problem) .In sum, this patient showed combination of aphasia, agrammatism, and right hemisphere damage( pragmatic deficit) together.