Arousal-dependent auditory response in the brain of Bengalese finches as measured by gene expression

Songbirds use auditory feedback to maintain their own songs. Juveniles also memorize a tutor song and use memory as a template to make up their own songs through auditory feedback. A recent electrophysiological study revealed that HVC neurons respond to BOS playback only in low arousal, sleeping, or anesthetized conditions. One outstanding question is how does auditory suppression occur in the brain? Here, we determined how arousal affects auditory responses simultaneously in the whole brain and over the song neural circuit in Bengalese finches, using the immediate early gene egr-1 as a marker of neural activity. Our results showed that auditory responses in the low-arousal state were less susceptible to gating, which was also confirmed by gene expression, and that the suppression may be weaker than observed in previous zebra finch studies. This may be because the Bengalese finch is a domesticated species. In addition, our results suggest that information may flow from the MLd.I of the midbrain to higher auditory regions. Altogether, this study presents a new attempt to explore the auditory suppression network by simultaneously investigating the whole brain using molecular biology methods.

Evaluation of Auditory Enhancement and Auditory Suppression in Listeners With Normal Hearing and Reduced Speech Recognition in Noise

A number of individuals complain of difficulties with speech recognition in noise in spite of normal hearing. This has prompted a search for disruptions in other areas of auditory processing that may account for these deficits. Two processes that may be related to speech recognition, auditory suppression and auditory enhancement, were evaluated in five listeners with normal speech recognition in noise (NSRN) and five listeners with reduced speech recognition in noise (RSRN). Although differences between the two groups were not observed for enhanced forward masking, significant differences were observed in two-tone suppression when the duration of the suppressor was varied. Those with RSRN showed greater suppression than those with NSRN when the suppressor onset preceded the masker onset.

Behavioral Disorders in Association with Posterior Callosal and Frontal Cerebral Infarction

Behavioral disorders were a prominent clinical feature after the surgical treatment of an anterior communicating artery aneurysm rupture in a 44-year-old man. Callosal apraxia was associated with an alien hand. The latter remained 1 year after surgery while diagonistic apraxia disappeared after 3 months. Other callosal signs included left agraphia, tactile anomia and auditory suppression. MRI revealed posterior callosal infarction and a right frontal infarct. The association of diagonistic apraxia and alien hand is rarely reported.