scholarly journals Top-down, contextual entrainment of neuronal oscillations in the auditory thalamocortical circuit

2018 ◽  
Vol 115 (32) ◽  
pp. E7605-E7614 ◽  
Author(s):  
Annamaria Barczak ◽  
Monica Noelle O’Connell ◽  
Tammy McGinnis ◽  
Deborah Ross ◽  
Todd Mowery ◽  
...  
Keyword(s):  
Nonhuman Primates ◽  
Temporal Structure ◽  
Neural Correlates ◽  
Neuronal Firing ◽  
Pattern Perception ◽  
Thalamic Nuclei ◽  
Top Down ◽  
Neuronal Oscillations ◽  
External Cues ◽  
Medial Geniculate

Prior studies have shown that repetitive presentation of acoustic stimuli results in an alignment of ongoing neuronal oscillations to the sequence rhythm via oscillatory entrainment by external cues. Our study aimed to explore the neural correlates of the perceptual parsing and grouping of complex repeating auditory patterns that occur based solely on statistical regularities, or context. Human psychophysical studies suggest that the recognition of novel auditory patterns amid a continuous auditory stimulus sequence occurs automatically halfway through the first repetition. We hypothesized that once repeating patterns were detected by the brain, internal rhythms would become entrained, demarcating the temporal structure of these repetitions despite lacking external cues defining pattern on- or offsets. To examine the neural correlates of pattern perception, neuroelectric activity of primary auditory cortex (A1) and thalamic nuclei was recorded while nonhuman primates passively listened to streams of rapidly presented pure tones and bandpass noise bursts. At arbitrary intervals, random acoustic patterns composed of 11 stimuli were repeated five times without any perturbance of the constant stimulus flow. We found significant delta entrainment by these patterns in the A1, medial geniculate body, and medial pulvinar. In A1 and pulvinar, we observed a statistically significant, pattern structure-aligned modulation of neuronal firing that occurred earliest in the pulvinar, supporting the idea that grouping and detecting complex auditory patterns is a top-down, context-driven process. Besides electrophysiological measures, a pattern-related modulation of pupil diameter verified that, like humans, nonhuman primates consciously detect complex repetitive patterns that lack physical boundaries.

Structural Changes in Thalamic Nuclei Across Prodromal and Clinical Alzheimer’s Disease

2021 ◽  
pp. 1-11
Author(s):  
Adam S. Bernstein ◽  
Steven Z. Rapcsak ◽  
Michael Hornberger ◽  
Manojkumar Saranathan ◽  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Large Scale ◽  
Structural Changes ◽  
Thalamic Nuclei ◽  
Medial Temporal Lobes ◽  
Cognitive Changes ◽  
Temporal Lobes ◽  
Medial Geniculate ◽  
Healthy Control

Background: Increasing evidence suggests that thalamic nuclei may atrophy in Alzheimer’s disease (AD). We hypothesized that there will be significant atrophy of limbic thalamic nuclei associated with declining memory and cognition across the AD continuum. Objective: The objective of this work was to characterize volume differences in thalamic nuclei in subjects with early and late mild cognitive impairment (MCI) as well as AD when compared to healthy control (HC) subjects using a novel MRI-based thalamic segmentation technique (THOMAS). Methods: MPRAGE data from the ADNI database were used in this study (n = 540). Healthy control (n = 125), early MCI (n = 212), late MCI (n = 114), and AD subjects (n = 89) were selected, and their MRI data were parcellated to determine the volumes of 11 thalamic nuclei for each subject. Volumes across the different clinical subgroups were compared using ANCOVA. Results: There were significant differences in thalamic nuclei volumes between HC, late MCI, and AD subjects. The anteroventral, mediodorsal, pulvinar, medial geniculate, and centromedian nuclei were significantly smaller in subjects with late MCI and AD when compared to HC subjects. Furthermore, the mediodorsal, pulvinar, and medial geniculate nuclei were significantly smaller in early MCI when compared to HC subjects. Conclusion: This work highlights nucleus specific atrophy within the thalamus in subjects with early and late MCI and AD. This is consistent with the hypothesis that memory and cognitive changes in AD are mediated by damage to a large-scale integrated neural network that extends beyond the medial temporal lobes.

scholarly journals Causal Evidence for the Role of Neuronal Oscillations in Top–Down and Bottom–Up Attention

2019 ◽  
Vol 31 (5) ◽  
pp. 768-779 ◽  
Author(s):  
Justin Riddle ◽  
Kai Hwang ◽  
Dillan Cellier ◽  
Sofia Dhanani ◽  
Mark D'Esposito
Keyword(s):  
Visual Field ◽  
Conjunction Search ◽  
Intraparietal Sulcus ◽  
Top Down ◽  
Neuronal Oscillations ◽  
Bottom Up ◽  
Search Condition ◽  
Gamma Frequency ◽  
Task Conditions ◽  
Beta Frequency

Beta and gamma frequency neuronal oscillations have been implicated in top–down and bottom–up attention. In this study, we used rhythmic TMS to modulate ongoing beta and gamma frequency neuronal oscillations in frontal and parietal cortex while human participants performed a visual search task that manipulates bottom–up and top–down attention (single feature and conjunction search). Both task conditions will engage bottom–up attention processes, although the conjunction search condition will require more top–down attention. Gamma frequency TMS to superior precentral sulcus (sPCS) slowed saccadic RTs during both task conditions and induced a response bias to the contralateral visual field. In contrary, beta frequency TMS to sPCS and intraparietal sulcus decreased search accuracy only during the conjunction search condition that engaged more top–down attention. Furthermore, beta frequency TMS increased trial errors specifically when the target was in the ipsilateral visual field for the conjunction search condition. These results indicate that beta frequency TMS to sPCS and intraparietal sulcus disrupted top–down attention, whereas gamma frequency TMS to sPCS disrupted bottom–up, stimulus-driven attention processes. These findings provide causal evidence suggesting that beta and gamma oscillations have distinct functional roles for cognition.

Cortical and Collicular Inputs to Cells in the Rat Paralaminar Thalamic Nuclei Adjacent to the Medial Geniculate Body

2007 ◽  
Vol 98 (2) ◽  
pp. 681-695 ◽  
Author(s):  
Philip H. Smith ◽  
Edward L. Bartlett ◽  
Anna Kowalkowski
Keyword(s):  
Conditioned Fear ◽  
Medial Geniculate Body ◽  
Cortical Layer ◽  
Axon Collateral ◽  
Thalamic Nuclei ◽  
Paired Pulse ◽  
Cortical Input ◽  
Spike Number ◽  
Medial Geniculate ◽  
Cortical Inputs

The paralaminar nuclei, including the medial division of the medial geniculate nucleus, surround the auditory thalamus medially and ventrally. This multimodal area receives convergent inputs from auditory, visual, and somatosensory structures and sends divergent outputs to cortical layer 1, amygdala, basal ganglia, and elsewhere. Studies implicate this region in the modulation of cortical 40-Hz oscillations, cortical information binding, and the conditioned fear response. We recently showed that the basic anatomy and intrinsic physiology of paralaminar cells are unlike that of neurons elsewhere in sensory thalamus. Here we evaluate the synaptic inputs to paralaminar cells from the inferior and superior colliculi and the cortex. Combined physiological and anatomical evidence indicates that paralaminar cells receive both excitatory and inhibitory inputs from both colliculi and excitatory cortical inputs. Excitatory inputs from all three sources typically generate small summating EPSPs composed of AMPA and NMDA components and terminate primarily on smaller dendrites and occasionally on dendritic spines. The cortical input shows strong paired-pulse facilitation (PPF), whereas both collicular inputs show weak PPF or paired-pulse depression (PPD). EPSPs of cells with no low-threshold calcium conductance do not evoke a burst response when the cell is hyperpolarized. Longer-latency EPSPs were seen and our evidence indicates that these arise from axon collateral inputs of other synaptically activated paralaminar cells. The inhibitory collicular inputs are GABAergic, activate GABAA receptors, and terminate on dendrites. Their activation can greatly alter EPSP-generated spike number and timing.

scholarly journals Neural correlates of top-down guidance of attention to food: An fMRI study

2020 ◽  
Vol 225 ◽  
pp. 113085
Author(s):  
Maartje S. Spetter ◽  
Suzanne Higgs ◽  
Dirk Dolmans ◽  
Jason M. Thomas ◽  
Renate L.E.P. Reniers ◽  
...  
Keyword(s):  
Neural Correlates ◽  
Top Down ◽  
Fmri Study

Sources of Somatosensory Input to the Caudal Belt Areas of Auditory Cortex

Perception ◽  
10.1068/p5841 ◽  
2007 ◽  
Vol 36 (10) ◽  
pp. 1419-1430 ◽  
Author(s):  
Troy A Hackett ◽  
John F Smiley ◽  
Istvan Ulbert ◽  
George Karmos ◽  
Peter Lakatos ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Nonhuman Primates ◽  
Superior Temporal Gyrus ◽  
Cortical Areas ◽  
Neuron Response ◽  
Cortical Connections ◽  
Somatosensory Input ◽  
Multisensory Convergence ◽  
Medial Geniculate ◽  
Somatic Input

The auditory cortex of nonhuman primates is comprised of a constellation of at least twelve interconnected areas distributed across three major regions on the superior temporal gyrus: core, belt, and parabelt. Individual areas are distinguished on the basis of unique profiles comprising architectonic features, thalamic and cortical connections, and neuron response properties. Recent demonstrations of convergent auditory – somatosensory interactions in the caudomedial (CM) and caudolateral (CL) belt areas prompted us to pursue anatomical studies to identify the source(s) of somatic input to auditory cortex. Corticocortical and thalamocortical connections were revealed by injecting neuroanatomical tracers into CM, CL, and adjoining fields of marmoset ( Callithrix jacchus jacchus) and macaque ( Macaca mulatta) monkeys. In addition to auditory cortex, the cortical connections of CM and CL included somatosensory (retroinsular, Ri; granular insula, Ig) and multisensory areas (temporal parietal occipital, temporal parietal temporal). Thalamic inputs included the medial geniculate complex and several multisensory nuclei (supra- geniculate, posterior, limitans, medial pulvinar), but not the ventroposterior complex. Injections of the core (A1, R) and rostromedial areas of auditory cortex revealed sparse multisensory connections. The results suggest that areas Ri and Ig are the principle sources of somatosensory input to the caudal belt, while multisensory regions of cortex and thalamus may also contribute. The present data add to growing evidence of multisensory convergence in cortical areas previously considered to be ‘unimodal’, and also indicate that auditory cortical areas differ in this respect.

scholarly journals Target Interneuron Preference in Thalamocortical Pathways Determines the Temporal Structure of Cortical Responses

2018 ◽  
Vol 29 (7) ◽  
pp. 2815-2831 ◽  
Author(s):  
Y Audrey Hay ◽  
Jérémie Naudé ◽  
Philippe Faure ◽  
Bertrand Lambolez
Keyword(s):  
Temporal Structure ◽  
Sensory Information ◽  
Response Duration ◽  
Cortical Response ◽  
Inhibitory Neurons ◽  
Thalamic Nuclei ◽  
Response Dynamics ◽  
Mean Field Model ◽  
Local Circuits ◽  
Feedforward Inhibition

Abstract Sensory processing relies on fast detection of changes in environment, as well as integration of contextual cues over time. The mechanisms by which local circuits of the cerebral cortex simultaneously perform these opposite processes remain obscure. Thalamic “specific” nuclei relay sensory information, whereas “nonspecific” nuclei convey information on the environmental and behavioral contexts. We expressed channelrhodopsin in the ventrobasal specific (sensory) or the rhomboid nonspecific (contextual) thalamic nuclei. By selectively activating each thalamic pathway, we found that nonspecific inputs powerfully activate adapting (slow-responding) interneurons but weakly connect fast-spiking interneurons, whereas specific inputs exhibit opposite interneuron preference. Specific inputs thereby induce rapid feedforward inhibition that limits response duration, whereas, in the same cortical area, nonspecific inputs elicit delayed feedforward inhibition that enables lasting recurrent excitation. Using a mean field model, we confirm that cortical response dynamics depends on the type of interneuron targeted by thalamocortical inputs and show that efficient recruitment of adapting interneurons prolongs the cortical response and allows the summation of sensory and contextual inputs. Hence, target choice between slow- and fast-responding inhibitory neurons endows cortical networks with a simple computational solution to perform both sensory detection and integration.

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