Right Hemisphere: Role in Recovery By Emily Seidman & Peter Peloquin

RH To The RESCUE RH LH

Figure 1: Location of the Language Areas of the Brain

Barlow Case Study 1877 Thomas Barlow, London physician, published a case of “functional speech recovery” following brain damage. The case involved a ten year old boy who had lost his speech, regained it, and then lost it again. Post-mortem studies of brain revealed morphological changes in brain volume in Broca’s increases in calcified brain nodules in the left facial motor area These morphological changes also were seen in the right hemisphere. Barlow’s case provoked subsequent investigations on the possible “takeover” functions of the right hemisphere.

New Procedures and Tests Only recently has the role of the right hemisphere in language processing been studied thoroughly (Finger 2003). New neurological procedures and scans have enabled researchers to study speech after unilateral and bilateral brain lesions. One of the first tests, The Wada test, involves injecting a barbiturate into the carotid artery that leads to one side of the brain. An injection of carotid into the left side of the brain carotid results in severely impaired speech production in 97% of the population. However, a right-sided carotid injection was found to inhibit speech in patients with left-hemisphere damage extending into Broca’s area.

Role of RH It has been hypothesized that although the right hemisphere plays a small role in speech production, the right hemisphere acquires the ability to regulate speech more effectively when the language areas of the left-hemisphere are damaged. A case of functional recovery: The role of right frontal activation Finger et al reported additional evidence for the increased speech production capabilities of the right hemisphere after left hemispheric damage. The study consisted one non-fluent aphasiac, who had most of the damage in the left frontal cortex near Broca’s area. His aphasia was labeled “incomplete” because he continued to do well on word generation tasks which normally activate the area he had sustained damage to, the frontal cortex.

Figure 2: A case of functional recovery; The role of right frontal activation (a) (b) (c) Part (a) of represents PET-scans of the coronal sections of a healthy individual performing a speech production task. Part (b) shows a structural MRI of a lesion to the frontal region (Broca’s Area) of a patient who has suffered a stroke. Part (c) shows a PET scan of the same patient during a speech production task. The right frontal activation is prominent in the patient post-stroke. Researchers believe that right frontal activation could be one of many mechanisms accounting for speech recovery.

Conclusions In patients with LH lesions, PET-scans revealed abnormally high activation of the right frontal brain regions. This evidence indicates that the patient’s preserved word generation abilities may be due to the recruitment of right-frontal regions. Other studies also have shown increased right-frontal activation during word generation tasks six months to one year after stroke. The right frontal activation is pronounced in the patient post-stroke. Therefore, researchers believe that right frontal activation may play a critical role in speech recovery in patients with LH lesions.

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