Determination of tonotopic maps in auditory cortex
A systematic recording from neuron best frequency (characteristic frequency) across regions of auditory cortex reveals cortical frequency maps. We have investigated various aspects of such tonotopic maps in cat and chinchilla animal models.
HARRISON, R.V., NAGASAWA A., SMITH D.W, STANTON S. and MOUNT R.J. (1991): Reorganization of auditory cortex after neonatal high frequency cochlear hearing loss. Hearing Research, 54, 11 -19.
HARRISON, R.V., KAKIGI, A., HIRAKAWA, H., HAREL, N., and MOUNT, R.J.: (1996) Tonotopic mapping in chinchilla auditory cortex. Hearing Research 100, 157-163.
PIENKOWSKI M, HARRISON RV. (2005). Tone frequency maps and receptive fields in developing chinchilla auditory cortex. J Neurophysiol. 93: 454-466
Cerebral blood flow changes and neural activity patterns
We have explored the relationship between neural activity in the auditory cortex and changes in local blood flow caused by the metabolic demands of neurons. We have used optical imaging of intrinsic signals in animals with simultaneous single unit recordings. Optical imaging measures aspects of blood flow similar to the BOLD effect in fMRI methods.
HARRISON, R.V., N. HAREL, H. HAMRAHI, J.PANESAR, N. MORI, and R. J. MOUNT (2000) Local Hemodynamic Changes Associated with Neural Activity in Auditory Cortex. Acta Otolaryngol 120:255-258
HAREL N, MORI N, SAWADA S, MOUNT RJ, HARRISON, R.V. (2000): Three distinct auditory areas of cortex (AI, AII, AAF) defined by optical imaging of intrinsic signals. NeuroImage 11:302-312
PANESAR J, HAMRAHI H, HAREL N, MORI N, MOUNT RJ, HARRISON, R.V. (2001) Arterial blood supply to auditory cortex of the chinchilla. Act Otolaryngol 121 839-843
HARRISON, R.V., HAREL N, PANESAR J, MOUNT RJ (2002) Blood capillary distribution correlates with hemodynamic based functional imaging in cerebral cortex. Cerebral Cortex. 12, 225-233.
Frequency coding in the auditory midbrain
In the central nucleus of the inferior colliculus (IC) of the midbrain a clear tonotopic frequency map can be assessed using single unit recordings of neuron characteristic frequency. In this example, note the map in the chinchilla model.
HARRISON, R.V., IBRAHIM D, MOUNT RJ. (1998): Plasticity of tonotopic maps in auditory midbrain following partial cochlear damage in the developing chinchilla. Exp Brain Res 123; 449-460.
D’ALESSANDRO L, HARRISON RV. (2014) Excitatory and inhibitory tonotopic bands in chinchilla inferior colliculus revealed by c-fos immuno-labeling. Hear Res Oct; 316:122-8
Developmental plasticity of tonotopic maps in cortex
We have studied the neuroplasticity of frequency maps in auditory cortex by mapping tonotopic regions of cortex with singe unit recordings. We have noted the changes to such maps in subjects resulting from neonatal changes to cochlear activity patterns.
HARRISON, R.V., NAGASAWA A., SMITH D.W, STANTON S. and MOUNT R.J. (1991): Reorganization of auditory cortex after neonatal high frequency cochlear hearing loss. Hearing Research, 54, 11 -19.
STANTON, S.G. and HARRISON, R.V. (1996): Abnormal cochleotopic organization in the auditory cortex of cats reared in a frequency augmented environment. Auditory Neuroscience 2, 97-107
KAKIGI A, HIRAKAWA H, HAREL N, MOUNT RJ, HARRISON, R.V. (2000): Tonotopic mapping in auditory cortex of the adult chinchilla with amikacin induced cochlear lesions. Audiology 39:153-160
STANTON SG, HARRISON, R.V. (2000) Projections from the medial geniculate body to primary auditory cortex in neonatally deafened cats. J Comp Neurol 426: 117-129
Postnatal refinement of frequency coding in auditory cortex
Using single unit electrophysiology we have determined how frequency coding in (chinchilla) cortex changes from birth to maturity.
PIENKOWSKI M, HARRISON RV. (2005) Tone responses in core versus belt auditory cortex in the developing chinchilla. J Comp Neurol. Nov 7;492(1):101-9.
BROWN TA, HARRISON RV. (2010) Postnatal development of neuronal responses to frequency-modulated tones in chinchilla auditory cortex. Brain Res. 14;1309:29-39.
