We report improved ability to name pictures at 2 and 8 months after repetitive transcranial magnetic stimulation (rTMS) treatments to the pars triangularis portion of right Broca's homologue in a 57 year-old woman with severe nonfluent/global aphasia (6.5 years post left basal ganglia bleed, subcortical lesion). TMS was applied at 1 Hz, 20 minutes a day, 10 days, over a two-week period. She received no speech therapy during the study. One year after her TMS treatments, she entered speech therapy with continued improvement. TMS may have modulated activity in the remaining left and right hemisphere neural network for naming.

Fifty years ago Gazzaniga and coworkers published a seminal article that discussed the separate roles of the cerebral hemispheres in humans. Today, the study of interhemispheric communication is facilitated by a battery of novel data analysis techniques drawn from across disciplinary boundaries, including dynamic systems theory and network theory. These techniques enable the characterization of dynamic changes in the brain's functional connectivity, thereby providing an unprecedented means of decoding interhemispheric communication. Here, we illustrate the use of these techniques to examine interhemispheric coordination in healthy human participants performing a split visual field experiment in which they process lexical stimuli. We find that interhemispheric coordination is greater when lexical information is introduced to the right hemisphere and must subsequently be transferred to the left hemisphere for language processing than when it is directly introduced to the language-dominant (left) hemisphere. Further, we find that putative functional modules defined by coherent interhemispheric coordination come online in a transient manner, highlighting the underlying dynamic nature of brain communication. Our work illustrates that recently developed dynamic, network-based analysis techniques can provide novel and previously unapproachable insights into the role of interhemispheric coordination in cognition.T he field of split-brain research began several decades ago with the use of a drastic surgical solution for intractable epilepsy (1-3): the severing of the corpus callosum. This procedure significantly decreased the connectivity between the hemispheres, thereby irrevocably altering interhemispheric communication. Although a few interhemispheric pathways remained through subcortical structures and the anterior commissure, examination of callosal function using split visual field experiments clearly demonstrated its role in interhemispheric communication (2). The callosal projection plays a particularly crucial role in a variety of sensory-motor integrative functions of the two hemispheres (4), shows changes with age, and demonstrates the potential for dynamic changes with training (5). In fact, experiments in patients with severance of the callosum revealed that it subserves a large range of behaviors and cognitive functions that underlie the varied workings of the mind.Interhemispheric communication has been studied using two basic approaches. The first uses behavioral experiments to examine cognitive phenotypes, and the second uses neuroscientific experiments to examine brain phenotypes. Split-brain research initially focused on the former: Patients demonstrated striking behavioral phenotypes that provided clues regarding the underlying mechanics of brain communication. For example, although most perceptual processing appears to be isolated in each hemisphere following surgery, some attentional and emotional mechanisms initiated in one hemisphere can still be communicated to the other, cortically disconnected,...

Functional brain imaging with nonfluent aphasia patients has shown increased cortical activation (perhaps "overactivation") in right (R) hemisphere language homologues. These areas of overactivation may represent a maladaptive strategy that interferes with, rather than promotes, aphasia recovery. Repetitive transcranial magnetic stimulation (rTMS) is a painless, noninvasive procedure that utilizes magnetic fields to create electric currents in discrete brain areas affecting about a 1-cm square area of cortex. Slow frequency, 1 Hz rTMS reduces cortical excitability. When rTMS is applied to an appropriate cortical region, it may suppress the possible overactivation and thus modulate a distributed neural network for language. We provide information on rTMS and report preliminary results following rTMS application to R Broca's area (posterior, R pars triangularis) in four stroke patients with nonfluent aphasia (5-11 years after left hemisphere stroke). Following 10 rTMS treatments, significant improvement in naming pictures was observed. This form of rTMS may provide a novel, complementary treatment for aphasia.

Two chronic, nonfluent aphasia patients participated in overt naming fMRI scans, pre-and post-a series of repetitive transcranial magnetic stimulation (rTMS) treatments as part of a TMS study to improve naming. Each patient received ten, 1-Hz rTMS treatments to suppress a part of R pars triangularis. P1 was a 'good responder' with improved naming and phrase length; P2 was a 'poor responder' without improved naming.Pre-TMS (10 yr. poststroke), P1 had significant activation in R and L sensorimotor cortex, R IFG, and in both L and R SMA during overt naming fMRI (28% pictures named. At 3 mo. post-TMS (42% named), P1 showed continued activation in R and L sensorimotor cortex, R IFG, and in R and L SMA. At 16 mo. post-TMS (58% named), he also showed significant activation in R and L sensorimotor cortex mouth and R IFG. He now showed a significant increase in activation in the L SMA compared to pre-TMS and at 3 mo. post-TMS (p<.02; p<.05, respectively). At 16 mo. there was also greater activation in L than R SMA (p<.08). At 46 mo. post-TMS (42% named), this new LH pattern of activation continued. He improved on the Boston Naming Test from 11 pictures named pre-TMS, to scores ranging from 14-18 pictures, post-TMS (2 mo. to 43 mo. post-TMS). His longest phrase length (Cookie Theft picture) improved from 3 words pre-TMS, to 5-6 words post-TMS.Pre-TMS (1.5 yr. poststroke), P2 had significant activation in R IFG (3% pictures named). At 3 and 6 mo. post-TMS, there was no longer significant activation in R IFG, but significant activation was present in R sensorimotor cortex. On all three fMRI scans, P2 had significant activation in both the L and R SMA. There was no new, lasting perilesional LH activation across sessions for this patient. Over time, there was little or no change in his activation. His naming remained only at 1-2 pictures during all three fMRI scans. His BNT score and longest phrase length remained at 1 word, post-TMS.Lesion site may play a role in each patient's fMRI activation pattern and response to TMS treatment. P2, the poor responder, had an atypical frontal lesion in the L motor and premotor cortex that extended Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The fMRI data of our patient who had good response following TMS support the notion that restoration of the LH language network is linked in part, to better recovery of naming and phrase length in nonfluent aphasia. NIH Public Access

In addition to its role in motor control, reflex adaptation, and motor learning, three sorts of evidence have been put forward to support the idea that the cerebellum may also be involved in cognition. Patients with cerebellar lesions are reported to have deficits in performing one or another cognitive task. The cerebellum is often seen to be activated when normal subjects perform such tasks. There are connections to and from areas of the prefrontal cortex that may be involved in cognition. In this paper, we review the anatomical evidence to support the claim. We suggest that there are only minor connections with cognitive areas of the cerebral cortex and that some of the imaging evidence may reflect the cerebellum's role in the control of eye movements rather than cognition.

No abstract

The corpus callosum is the largest white matter pathway in the human brain. The most posterior portion, known as the splenium, is critical for interhemispheric communication between visual areas. The current study employed diffusion tensor imaging to delineate the complete cortical projection topography of the human splenium. Homotopic and heterotopic connections were revealed between the splenium and the posterior visual areas, including the occipital and the posterior parietal cortices. In nearly one third of participants, there were homotopic connections between the primary visual cortices, suggesting interindividual differences in splenial connectivity. There were also more instances of connections with the right hemisphere, indicating a hemispheric asymmetry in interhemispheric connectivity within the splenium. Combined, these findings demonstrate unique aspects of human interhemispheric connectivity and provide anatomical bases for hemispheric asymmetries in visual processing and a long-described hemispheric asymmetry in speed of interhemispheric communication for visual information.

Two chronic, nonfluent aphasia patients participated in overt naming fMRI scans, pre-and post-a series of repetitive transcranial magnetic stimulation (rTMS) treatments as part of a TMS study to improve naming. Each patient received ten, 1-Hz rTMS treatments to suppress a part of R pars triangularis. P1 was a 'good responder' with improved naming and phrase length; P2 was a 'poor responder' without improved naming.Pre-TMS (10 yr. poststroke), P1 had significant activation in R and L sensorimotor cortex, R IFG, and in both L and R SMA during overt naming fMRI (28% pictures named. At 3 mo. post-TMS (42% named), P1 showed continued activation in R and L sensorimotor cortex, R IFG, and in R and L SMA. At 16 mo. post-TMS (58% named), he also showed significant activation in R and L sensorimotor cortex mouth and R IFG. He now showed a significant increase in activation in the L SMA compared to pre-TMS and at 3 mo. post-TMS (p<.02; p<.05, respectively). At 16 mo. there was also greater activation in L than R SMA (p<.08). At 46 mo. post-TMS (42% named), this new LH pattern of activation continued. He improved on the Boston Naming Test from 11 pictures named pre-TMS, to scores ranging from 14-18 pictures, post-TMS (2 mo. to 43 mo. post-TMS). His longest phrase length (Cookie Theft picture) improved from 3 words pre-TMS, to 5-6 words post-TMS.Pre-TMS (1.5 yr. poststroke), P2 had significant activation in R IFG (3% pictures named). At 3 and 6 mo. post-TMS, there was no longer significant activation in R IFG, but significant activation was present in R sensorimotor cortex. On all three fMRI scans, P2 had significant activation in both the L and R SMA. There was no new, lasting perilesional LH activation across sessions for this patient. Over time, there was little or no change in his activation. His naming remained only at 1-2 pictures during all three fMRI scans. His BNT score and longest phrase length remained at 1 word, post-TMS.Lesion site may play a role in each patient's fMRI activation pattern and response to TMS treatment. P2, the poor responder, had an atypical frontal lesion in the L motor and premotor cortex that extended Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The fMRI data of our patient who had good response following TMS support the notion that restoration of the LH language network is linked in part, to better recovery of naming and phrase length in nonfluent aphasia. NIH Public Access