The effect of tDCS on functional connectivity in primary progressive aphasia.

Transcranial direct current stimulation (tDCS) is an innovative technique recently shown to improve language outcomes even in neurodegenerative conditions such as primary progressive aphasia (PPA), but the underlying brain mechanisms are not known. The present study tested whether the additional language gains with repetitive tDCS (over sham) in PPA are caused by changes in functional connectivity between the stimulated area (the left inferior frontal gyrus (IFG)) and the rest of the language network. We scanned 24 PPA participants (11 female) before and after language intervention (written naming/spelling) with a resting-state fMRI sequence and compared changes before and after three weeks of tDCS or sham coupled with language therapy. We correlated changes in the language network as well as in the default mode network (DMN) with language therapy outcome measures (letter accuracy in written naming). Significant tDCS effects in functional connectivity were observed between the stimulated area and other language network areas and between the language network and the DMN. TDCS over the left IFG lowered the connectivity between the above pairs. Changes in functional connectivity correlated with improvement in language scores (letter accuracy as a proxy for written naming) evaluated before and after therapy. These results suggest that one mechanism for anodal tDCS over the left IFG in PPA is a decrease in functional connectivity (compared to sham) between the stimulated site and other posterior areas of the language network. These results are in line with similar decreases in connectivity observed after tDCS over the left IFG in aging and other neurodegenerative conditions.

Impaired emotion processing from vocal and facial cues in frontotemporal dementia compared to right hemisphere stroke.

To advance our understanding about the emotional and cognitive deficits of patients with frontotemporal dementia with behavioral variant (bvFTD), the current study examined comprehension and expression of emotions from prosodic and facial cues in a 66-year-old woman. The patient diagnosed with bvFTD is compared to six patients with acute right hemisphere stroke. Recognition of emotion from prosodic cues was assessed using an identification task in four conditions with decreasing verbal demands (neutral sentences, language-like pseudo sentences, monosyllables, and asyllabic vowel sounds). Repetition of utterances with emotional connotations and self-generated conversations were analyzed to measure relative changes in mean fundamental frequency (f0), f0 variance, speech rate, and intensity along with the facial musculature pattern. The patient showed a marked deficit in identifying emotions in all four prosody conditions; and she did not show much variation in modulating mean f0, f0 variance, speech rate and intensity for all emotion categories when compared to neutral utterances. In addition, this patient demonstrated little to no facial expressions during emotionally provoking tasks, but demonstrated no difficulty recognizing emotions from facial expressions or verbal scenarios. Results show that the patient seems to have selective impairment in recognition of emotions from prosody and expression of emotions using both prosodic and facial features. Impaired processing of emotional prosody and facial expressions could be important for detecting bvFTD with greater right hemisphere atrophy.

Relatively normal repetition performance despite severe disruption of the left arcuate fasciculus.

The arcuate fasciculus (AF) is believed to be fundamental to the neural circuitry behind many important cognitive processes. Connecting Wernicke's and Broca's area, these fibers are thought to be especially important for repetition. In this case study we present evidence from a patient that set doubt on these assumptions. We present structural imaging, diffusion tensor imaging, and language data on a patient with a large left-sided stroke and severely damaged left AF who showed intact word repetition and relatively intact sentence repetition performance. Specifically, his sentence repetition is more fluent and grammatical, with less hesitation than spontaneous speech, and with rare omissions only during the longest sentences. These results challenge classical theories that maintain the left AF is the dominant language processing pathway or mechanism for repetition.

Pathogenesis, neuroimaging and management in children with cerebral palsy born preterm.

With advances in obstetric and perinatal management, the incidence of intraventricular hemorrhage in premature infants has declined, while periventricular leukomalacia remains a significant concern. It is now known that brain injury in children born preterm also involves neuronal-axonal disease in supratentorial and infratentorial structures. The developing brain is especially vulnerable to white matter (WM) injury from 23 to 34 weeks gestation when blood vessels serving the periventricular WM are immature. Oligodendrocyte progenitors, which are beginning to form myelin during this time, are susceptible to attack from oxygen free radicals, glutamate, and inflammatory cytokines. Advances in imaging techniques such as diffusion tensor imaging provide a more complete picture of the location and extent of injury. Effective management of children born preterm with cerebral palsy is predicated on an understanding of sequential links from etiological antecedents to brain neuropathology as revealed with neuroimaging techniques to clinical phenotypes, toward focused interventions with measurable outcomes.