Auditory cortical stimulability in non habilitated individuals - An evidence from CAEPs.

Objective: The effect of long term auditory deprivation on Cortical Auditory Evoked Potentials (CAEPs) especially in human models is not well explored. Hence, the current study was aimed to investigate the effects of long-term auditory deprivation and stimulability of auditory cortex in non habilitated congenitally deaf adolescents and adults using CAEPs. Methods and Results: A total of 27 non-habilitated congenitally deaf adolescents/adults with age and gender matched normal hearing adolescents/adults participated in the study. The congenitally deaf group was fitted with high gain hearing aids (first fit). Further, the CAEPs were recorded. The obtained CAEP components were assessed for group effect, source and topographical differences. The between group analysis for CAEP responses showed a significant difference only for P2 latency and amplitude. The source analysis revealed that, in the normal hearing group for CAEPs, the sources were within the temporal regions. However, in the congenitally deaf group, along with the temporal cortex, the bilateral prefrontal cortex also was activated. Conclusion: The findings revealed that it is possible to stimulate and evoke a matured CAEP response from a long deprived auditory system with adequate acoustic stimulation. The presence of CAEP responses is indicative of the functionality of the innate auditory pathway and the crossmodal plasticity in long auditory deprived individuals.

The Effect of Intensity on the Speech Evoked Auditory Late Latency Response in Normal Hearing Individuals.

OBJECTIVE: Among the stimulus factors, the influence of presentation level is less studied in normal-hearing individuals when using speech stimuli withvarious presentation levels for the auditory late latency response (ALLR). Hence, the present study aimed to explore the Latency-Intensity (L-I) function, i.e., how the latency and amplitude change as a function of intensity using speech stimuli. MATERIALS AND METHODS: Speech-evoked ALLR was obtained from 15 normal-hearing individuals. The syllable/ta/ was used to record ALLR with an intensity of 30, 50, 70, and 90 dBSPL. Electroencephalography (EEG) from five channels was recorded and analyzed offline. RESULTS: The overall results revealed that there is an influence of intensity on P1 and N1 latencies in a nonlinear fashion. The latency change is consistent at lower intensities than at moderate and high intensities. The amplitude changes did not reach significance, though a decrease with a reduction in intensity was obvious. CONCLUSION: There is a significant effect of intensity on the latency and amplitude of ALLR in speech stimulus. However, this effect may vary for different speech stimuli.

Glucocorticoid receptor dysfunction: consequences for the pathophysiology and treatment of mood disorders.

BACKGROUND: Hypothalamic-pituitary-adrenal (HPA) axis dysfunction in mood disorders is one of the most robust findings in biological psychiatry. However, considerable debate surrounds the nature of the core abnormality, its cause, consequences and treatment implications. AIMS: To review the evidence for the role of HPA axis dysfunction in the pathophysiology of mood disorders with particular reference to corticosteroid receptor pathology. METHODS: A selective review of the published literature in this field, focusing on human studies. RESULTS: The nature of basal HPA axis dysregulation described in both manic and depressed bipolars appears to be similar to those described in MDD. But studies using the dexamethasone/ corticotropin releasing hormone (dex/CRH) test and dexamethasone suppression test (DST) have shown that HPA axis dysfunction is more prevalent in bipolar than in unipolar disorder. There is robust evidence for corticotropin releasing hormone (CRH) hyperdrive and glucocorticoid receptor (GR) dysfunction in mood disorders, with increasing evidence for disorders within the AVP system. CONCLUSION: HPA axis dysfunction is prevalent in patients with mood disorder, particularly those with psychotic disorders and bipolar affective disorder. This may be secondary to genetic factors, early life adversities or both. Dysfunction of GR may be the underlying abnormality and preliminary findings suggest that it is a potential target for novel therapies. DECLARATION OF INTEREST: None.