AUDITORY SYSTEM RESEARCH
My current research is focused on the development of vocalization-processing in the pallid bat auditory cortex. Vocalization-selective neurons are present in several vertebrate groups. It is known from songbird studies that experience plays an important role in the development of selectivity for vocalizations. However, because of the complex multi-syllabic and –harmonic nature of social communication calls, the mechanisms underlying selectivity for songs are not well understood. Mammalian models of vocalization-selectivity have also emphasized complex social communication calls. Due to the lack of understanding of the mechanisms through which selectivity arises it is unclear how selectivity changes during normal and abnormal development. This topic also has clinical implications due to its relevance to human language processing.
The pallid bat is a powerful model system in which the sound used for a specific behavior, the neural selectivity for that sound and the inhibitory mechanisms underlying selectivity have all been well studied. My current research addresses the following specific questions:
Selected publications
Razak KA and Fuzessery ZM (2007) Development of inhibitory mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the auditory cortex. Journal of Neuroscience 27:1769-1781 [pdf of article]
Razak KA and Fuzessery ZM (2007) Development of functional organization of the pallid bat auditory cortex. Hearing Research 228:69-81 [pdf of article]
Razak KA, Shen W, Zumsteg, T and Fuzessery, ZM (2006) Parallel thalamocortical pathways for echolocation and passive sound localization in a gleaning bat, Antrozous pallidus. Journal of Comparative Neurology 500:322-338, 2006 [pdf of article]
Razak KA and Fuzessery ZM (2006) Neural mechanisms underlying selectivity for the rate and direction of frequency-modulated sweeps in the auditory cortex of the pallid bat. Journal of Neurophysiology 96:1303–1319 [pdf of article]
Barber JR, Razak KA and Fuzessery ZM (2003) Can two streams of auditory information be processed simultaneously? Evidence from the gleaning bat Antrozous pallidus. Journal of Comparative Physiology A 189: 843-855.
Razak KA and Fuzessery ZM. Functional organization of the pallid bat auditory cortex: emphasis on binaural organization. J. Neurophysiol. 87(1): 72-86, 2002.
Razak KA and Fuzessery ZM. A systematic representation of interaural intensity differences in the auditory cortex of the pallid bat. NeuroReport 11(13): 2919-2924, 2000.
Razak KA, Fuzessery ZM and Lohuis T. Single neurons respond to both active and passive sounds in the pallid bat auditory cortex. J. Neurophysiol. 81(3): 1438-1442, 1999.