Evaluation of inputs to rat primary auditory cortex from the suprageniculate nucleus and extrastriate visual cortex

ABSTRACTAudiovisual speech perception relies, among other things, on our expertise to map a speaker’s lip movements with speech sounds. This multimodal matching is facilitated by salient syllable features that align lip movements and acoustic envelope signals in the 4 - 8 Hz theta band. Although non-exclusive, the predominance of theta rhythms in speech processing has been firmly established by studies showing that neural oscillations track the acoustic envelope in the primary auditory cortex. Equivalently, theta oscillations in the visual cortex entrain to lip movements, and the auditory cortex is recruited during silent speech perception. These findings suggest that neuronal theta oscillations may play a functional role in organising information flow across visual and auditory sensory areas. We presented silent speech movies while participants performed a pure tone detection task to test whether entrainment to lip movements directs the auditory system and drives behavioural outcomes. We showed that auditory detection varied depending on the ongoing theta phase conveyed by lip movements in the movies. In a complementary experiment presenting the same movies while recording participants’ electro-encephalogram (EEG), we found that silent lip movements entrained neural oscillations in the visual and auditory cortices with the visual phase leading the auditory phase. These results support the idea that the visual cortex entrained by lip movements filtered the sensitivity of the auditory cortex via theta phase synchronisation.

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Development of visual category selectivity in ventral visual cortex does not require visual experience

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1612862114 ◽

2017 ◽

Vol 114 (22) ◽

pp. E4501-E4510 ◽

Cited By ~ 53

Author(s):

Job van den Hurk ◽

Marc Van Baelen ◽

Hans P. Op de Beeck

Keyword(s):

Visual Cortex ◽

Auditory Cortex ◽

Visual Processing ◽

Visual Experience ◽

Temporal Cortex ◽

Primary Auditory Cortex ◽

Extrastriate Cortex ◽

Striking Similarity ◽

Visual Responses ◽

Blind Individuals

To what extent does functional brain organization rely on sensory input? Here, we show that for the penultimate visual-processing region, ventral-temporal cortex (VTC), visual experience is not the origin of its fundamental organizational property, category selectivity. In the fMRI study reported here, we presented 14 congenitally blind participants with face-, body-, scene-, and object-related natural sounds and presented 20 healthy controls with both auditory and visual stimuli from these categories. Using macroanatomical alignment, response mapping, and surface-based multivoxel pattern analysis, we demonstrated that VTC in blind individuals shows robust discriminatory responses elicited by the four categories and that these patterns of activity in blind subjects could successfully predict the visual categories in sighted controls. These findings were confirmed in a subset of blind participants born without eyes and thus deprived from all light perception since conception. The sounds also could be decoded in primary visual and primary auditory cortex, but these regions did not sustain generalization across modalities. Surprisingly, although not as strong as visual responses, selectivity for auditory stimulation in visual cortex was stronger in blind individuals than in controls. The opposite was observed in primary auditory cortex. Overall, we demonstrated a striking similarity in the cortical response layout of VTC in blind individuals and sighted controls, demonstrating that the overall category-selective map in extrastriate cortex develops independently from visual experience.

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Unidirectional monosynaptic connections from auditory areas to the primary visual cortex in the marmoset monkey

10.1101/373779 ◽

2018 ◽

Cited By ~ 2

Author(s):

Piotr Majka ◽

Marcello G. P. Rosa ◽

Shi Bai ◽

Jonathan M. Chan ◽

Bing-Xing Huo ◽

...

Keyword(s):

Visual Cortex ◽

Auditory Cortex ◽

Primary Visual Cortex ◽

Peripheral Vision ◽

Early Stage ◽

World Monkey ◽

Primary Auditory Cortex ◽

Audiovisual Integration ◽

Primate Species ◽

Retrograde Tracer

AbstractUntil the late 20th Century, it was believed that different sensory modalities were processed by largely independent pathways in the primate cortex, with cross-modal integration only occurring in specialized polysensory areas. This model was challenged by the finding that the peripheral representation of the primary visual cortex (V1) receives monosynaptic connections from areas of the auditory cortex in the macaque. However, auditory projections to V1 have not been reported in other primates. We investigated the existence of direct interconnections between V1 and auditory areas in the marmoset, a New World monkey. Labelled neurons in auditory cortex were observed following 4 out of 10 retrograde tracer injections involving V1. These projections to V1 originated in the caudal subdivisions of auditory cortex (primary auditory cortex, caudal belt and parabelt areas), and targeted parts of V1 that represent parafoveal and peripheral vision. Injections near the representation of the vertical meridian of the visual field labelled few or no cells in auditory cortex. We also placed 8 retrograde tracer injections involving core, belt and parabelt auditory areas, none of which revealed direct projections from V1. These results confirm the existence of a direct, nonreciprocal projection from auditory areas to V1 in a different primate species, which has evolved separately from the macaque for over 30 million years. The essential similarity of these observations between marmoset and macaque indicate that early-stage audiovisual integration is a shared characteristic of primate sensory processing.

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Different excitation-inhibition correlations between spontaneous and tone-evoked activity in primary auditory cortex neurons

10.1101/2021.12.20.473450 ◽

2021 ◽

Author(s):

Katherine C. M. Chew ◽

Vineet Kumar ◽

Andrew Y. Y. Tan

Keyword(s):

Visual Cortex ◽

Auditory Cortex ◽

Event Rate ◽

Primary Auditory Cortex ◽

Cell Voltage ◽

Tuning Curves ◽

Anesthetized Rats ◽

Visual Cortex Neurons ◽

Evoked Activity ◽

Highly Correlated

Tone-evoked synaptic excitation and inhibition are highly correlated in many neurons with V-shaped tuning curves in the primary auditory cortex of pentobarbital-anesthetized rats. In contrast, there is less correlation between spontaneous excitation and inhibition in visual cortex neurons under the same anesthetic conditions. However, it was not known whether the primary auditory cortex resembles visual cortex in having spontaneous excitation and inhibition that is less correlated than tone-evoked excitation and inhibition. Here we report whole-cell voltage-clamp measurements of spontaneous excitation and inhibition in primary auditory cortex neurons of pentobarbital-anesthetized rats. The larger excursions of both spontaneous excitatory and inhibitory currents appeared to consist of distinct events, with the inhibitory event rate typically lower than the excitatory event rate. We use the ratio of the excitatory event rate to the inhibitory event rate, and the assumption that the excitatory and inhibitory synaptic currents can each be reasonably described as a filtered Poisson process, to estimate the maximum spontaneous excitatory-inhibitory correlation for each neuron. In a subset of neurons, we also measured tone-evoked excitation and inhibition. In neurons with V-shaped tuning curves, although tone-evoked excitation and inhibition were highly correlated, the spontaneous inhibitory event rate was typically sufficiently lower than the spontaneous excitatory event rate to indicate a lower excitatory-inhibitory correlation for spontaneous activity than for tone-evoked responses.

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The future of mapping sensory cortex in primates: three of many remaining issues

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2005.1624 ◽

2005 ◽

Vol 360 (1456) ◽

pp. 653-664 ◽

Cited By ~ 29

Author(s):

Jon H Kaas

Keyword(s):

Cerebral Cortex ◽

Visual Cortex ◽

Auditory Cortex ◽

Primary Auditory Cortex ◽

Sensory Cortex ◽

Cortical Processing ◽

Early Stages ◽

The Future ◽

Somatosensory Areas ◽

Area 3B

After 100 years of progress in understanding the organization of cerebral cortex, three issues have persisted over the last 35 years, which are revisited in this paper. First, is V3 an established or questionable area of visual cortex? Second, does taste cortex include part of area 3b (S1 proper) and other somatosensory areas? Third, is primary auditory cortex, A1, of primates the homologue of A1 in cats? The existence of such questions about even the early stages of cortical processing reflects the difficulties in mapping cerebral cortex, and reminds us that the era of basic discovery is far from over.

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