The authors thank Dr Robert H. Wurtz (NIH) for valuable comments on this manuscript. This research was supported in part by the JSPS Asian Core Program, the Ministry of Education, Science, Sports and Culture, a Grant-in-Aid for Scientific

Research (A) (22240051), and the National Bio-Resource Project (NBRP) ‘Japanese Monkeys’ of the MEXT, Japan. “
“Previous behavioural studies in human subjects have demonstrated the importance of amplitude modulations to the process of intelligible speech perception. SGI-1776 cost In functional neuroimaging studies of amplitude modulation processing, the inherent assumption is that all sounds are decomposed into simple building blocks, i.e. sinusoidal modulations. The encoding of complex and dynamic stimuli is often modelled to be the linear addition of a number of sinusoidal modulations and so, by investigating the response of the cortex to sinusoidal modulation, an experimenter can probe the same mechanisms used to encode speech. The experiment described in this paper used magnetoencephalography to measure the auditory steady-state response produced by six sounds, all modulated in amplitude at the same frequency but which formed a continuum from sinusoidal to pulsatile modulation. Analysis of the evoked response shows that the magnitude

of the envelope-following response is highly non-linear, with sinusoidal amplitude modulation producing the weakest steady-state response. Conversely, the phase of the steady-state response was related to the shape of the modulation waveform, with selleck compound the sinusoidal amplitude modulation producing the shortest latency relative to the other stimuli. It is shown that a point in auditory cortex produces a strong envelope following response to all stimuli on the continuum, but the timing of this response is related to the shape of the modulation waveform. The results suggest that steady-state response characteristics are L-NAME HCl determined by features of the waveform outside of the modulation domain and that the use of purely sinusoidal amplitude modulations may be misleading, especially in the context of speech encoding. “
“This

article describes the effects of dexmedetomidine (DEX) – the active ingredient of medetomidine, which is the latest popular sedative for functional magnetic resonance imaging (fMRI) in rodents – on multiple unit activity, local field potential (LFP), cerebral blood flow (CBF), pial vessel diameter [indicative of cerebral blood volume (CBV)], and blood oxygenation level-dependent (BOLD) fMRI. These measurements were obtained from the rat somatosensory cortex during 10 s of forepaw stimulation. We found that the continuous intravascular systemic infusion of DEX (50 μg/kg/h, doses typically used in fMRI studies) caused epileptic activities, and that supplemental isoflurane (ISO) administration of ~0.3% helped to suppress the development of epileptic activities and maintained robust neuronal and hemodynamic responses for up to 3 h.