Integration Of Auditory Information Research Articles

Age-Related Changes to Multisensory Integration and Audiovisual Speech Perception.

Multisensory integration is essential for the quick and accurate perception of our environment, particularly in everyday tasks like speech perception. Research has highlighted the importance of investigating bottom-up and top-down contributions to multisensory integration and how these change as a function of ageing. Specifically, perceptual factors like the temporal binding window and cognitive factors like attention and inhibition appear to be fundamental in the integration of visual and auditory information-integration that may become less efficient as we age. These factors have been linked to brain areas like the superior temporal sulcus, with neural oscillations in the alpha-band frequency also being implicated in multisensory processing. Age-related changes in multisensory integration may have significant consequences for the well-being of our increasingly ageing population, affecting their ability to communicate with others and safely move through their environment; it is crucial that the evidence surrounding this subject continues to be carefully investigated. This review will discuss research into age-related changes in the perceptual and cognitive mechanisms of multisensory integration and the impact that these changes have on speech perception and fall risk. The role of oscillatory alpha activity is of particular interest, as it may be key in the modulation of multisensory integration.

Abstinence following intermittent methylphenidate exposure dose-dependently modifies brain glucose metabolism in the rat brain.

Methylphenidate (MP) is a psychostimulant chronically prescribed for the treatment of attention deficit hyperactivity disorder (ADHD). Additionally, MP users may take breaks from using the medication during "drug holidays," which may include short-term or long-term breaks from medication. The present study utilized fluorodeoxyglucose (FDG) positron emission tomography (PET) to analyze the effects of chronic oral MP use and abstinence on brain glucose metabolism (BGluM) in rats at two different doses: high dose (HD) and low dose (LD). The schedule of treatment was 3weeks on-treatment and 1week off-treatment for a period of 13weeks, followed by an abstinence period of 4 total weeks. Results showed that chronic MP treatment using this schedule did not lead to significant changes in BGluM when comparing the control to HD MP groups. However, significant activation in BGluM was observed after periods of abstinence between control and HD MP rats in the following brain regions: the trigeminal nucleus, reticular nucleus, inferior olive, lemniscus, mesencephalic reticular formation, inferior colliculus, and several areas of the cerebellum. These brain regions and functional brain circuit play a role in facial sensory function, the auditory pathway, organizing connections between the thalamus and cortex, motor learning, auditory function, control over eye movement, auditory information integration, and both motor and cognitive functions. These results, when considered with previous studies, indicate that MP schedule of use may have differing effects on BGluM. BGluM following long-term MP use was dependent on MP dose and schedule of use in rats. This study was conducted in non-ADHD model rats with the aim to establish an understanding of the effects of MP itself, especially given the growing chronic off-label and prescribed use of MP. Further studies are needed for analysis of the drug's effects on an ADHD model.

Human-mimetic binaural ear design and sound source direction estimation for task realization of musculoskeletal humanoids

Human-like environment recognition by musculoskeletal humanoids is important for task realization in real complex environments and for use as dummies for test subjects. Humans integrate various sensory information to perceive their surroundings, and hearing is particularly useful for recognizing objects out of view or out of touch. In this research, we aim to realize human-like auditory environmental recognition and task realization for musculoskeletal humanoids by equipping them with a human-like auditory processing system. Humans realize sound-based environmental recognition by estimating directions of the sound sources and detecting environmental sounds based on changes in the time and frequency domain of incoming sounds and the integration of auditory information in the central nervous system. We propose a human mimetic auditory information processing system, which consists of three components: the human mimetic binaural ear unit, which mimics human ear structure and characteristics, the sound source direction estimation system, and the environmental sound detection system, which mimics processing in the central nervous system. We apply it to Musashi, a human mimetic musculoskeletal humanoid, and have it perform tasks that require sound information outside of view in real noisy environments to confirm the usefulness of the proposed methods.

P427. Sustained Negative Wave in Response to 40 Hz Auditory Stimulation in Rett Syndrome

Rett syndrome is a rare severe neurodevelopmental disorder caused by MECP2 gene disruption. Language impairments is one of the characteristics of the syndrome, although exact neurophysiological underpinnings of such problems are unknown. Our study examined sustained negative wave of electrophysiological response to 40-Hz auditory stimulation, which is suggested to underlie a language dysfunction and is associated with integration of auditory information into the unitary percept.

Human auditory frequency discrimination and inter-stimulus interval

The goal of this study was to determine how human performance in discriminating between similar frequencies in the auditory spectrum was influenced by modifying the interstimulus interval (ISI). The ISI is defined as the time elapsed from the end of the first stimulus and the beginning of the second stimulus. The relationship between ISI and auditory discrimination was explored using an auditory file comprised of 40 tests that each contained two tones with a frequency difference of 1%. For each test, 44 participants were asked to select the tone they perceived as being a higher frequency. The two frequencies used in each test were centered around one of five base frequencies, and the ISI used in each test was one of eight predetermined intervals. Results from previous auditory frequency discrimination studies regarding the just-noticeable difference (JND) and Weber’s law were used in the selection of the frequency difference of 1% that was used in this experiment. This frequency difference was kept constant across all the tests in order to ensure that the ISI was the main factor influencing participant performance. Participant performance was greatest at an ISI of 1000 ms when results were averaged by frequency. Additionally, as the base frequency increased, average performance generally improved. The findings from this experiment promote further investigation into the effects of varying ISI on the integration of auditory information by the auditory cortex.

Periodontal tactile input activates the prefrontal cortex.

The prefrontal cortex (PFC) plays a role in complex cognitive behavioural planning, decision-making, and social behaviours. However, the effects of sensory integration during motor tasks on PFC activation have not been studied to date. Therefore, we investigated the effect of peripheral sensory information and external information on PFC activation using functional near-infrared spectroscopy (fNIRS). Cerebral blood flow (CBF) was increased around bilateral Brodmann areas 46 and 10 during visual and auditory information integration during an occlusal force (biting) task. After local anesthesia, CBF values were significantly decreased, but occlusal force was similar. In conclusion, the effects of peripheral sensory information from the periodontal ligament and external information have minimal impacts on occlusal force maintenance but are important for PFC activation.

Temporal integration of auditory information as revealed by MMN and earlier evoked potential correlates: A preliminary study

Temporal integration of auditory information as revealed by MMN and earlier evoked potential correlates: A preliminary study

Bilateral collicular interaction: Modulation of auditory signal processing in frequency domain

In the ascending auditory pathway, the inferior colliculus (IC) receives and integrates excitatory and inhibitory inputs from a variety of lower auditory nuclei, intrinsic projections within the IC, contralateral IC through the commissure of the IC and the auditory cortex. All these connections make the IC a major center for subcortical temporal and spectral integration of auditory information. In this study, we examine bilateral collicular interaction in the modulation of frequency-domain signal processing of mice using electrophysiological recording and focal electrical stimulation. Focal electrical stimulation of neurons in one IC produces widespread inhibition and focused facilitation of responses of neurons in the other IC. This bilateral collicular interaction decreases the response magnitude and lengthens the response latency of inhibited IC neurons but produces an opposite effect on the response of facilitated IC neurons. In the frequency domain, the focal electrical stimulation of one IC sharpens or expands the frequency tuning curves (FTCs) of neurons in the other IC to improve frequency sensitivity and the frequency response range. The focal electrical stimulation also produces a shift in the best frequency (BF) of modulated IC (ICMdu) neurons toward that of electrically stimulated IC (ICES) neurons. The degree of bilateral collicular interaction is dependent upon the difference in the BF between the ICES neurons and ICMdu neurons. These data suggest that bilateral collicular interaction is a part of dynamic acoustic signal processing that adjusts and improves signal processing as well as reorganizes collicular representation of signal parameters according to the acoustic experience.

Bilateral Collicular Interaction: Modulation of Auditory Signal Processing in Amplitude Domain

In the ascending auditory pathway, the inferior colliculus (IC) receives and integrates excitatory and inhibitory inputs from many lower auditory nuclei, intrinsic projections within the IC, contralateral IC through the commissure of the IC and from the auditory cortex. All these connections make the IC a major center for subcortical temporal and spectral integration of auditory information. In this study, we examine bilateral collicular interaction in modulating amplitude-domain signal processing using electrophysiological recording, acoustic and focal electrical stimulation. Focal electrical stimulation of one (ipsilateral) IC produces widespread inhibition (61.6%) and focused facilitation (9.1%) of responses of neurons in the other (contralateral) IC, while 29.3% of the neurons were not affected. Bilateral collicular interaction produces a decrease in the response magnitude and an increase in the response latency of inhibited IC neurons but produces opposite effects on the response of facilitated IC neurons. These two groups of neurons are not separately located and are tonotopically organized within the IC. The modulation effect is most effective at low sound level and is dependent upon the interval between the acoustic and electric stimuli. The focal electrical stimulation of the ipsilateral IC compresses or expands the rate-level functions of contralateral IC neurons. The focal electrical stimulation also produces a shift in the minimum threshold and dynamic range of contralateral IC neurons for as long as 150 minutes. The degree of bilateral collicular interaction is dependent upon the difference in the best frequency between the electrically stimulated IC neurons and modulated IC neurons. These data suggest that bilateral collicular interaction mainly changes the ratio between excitation and inhibition during signal processing so as to sharpen the amplitude sensitivity of IC neurons. Bilateral interaction may be also involved in acoustic-experience-dependent plasticity in the IC. Three possible neural pathways underlying the bilateral collicular interaction are discussed.

Endocannabinoids Link Feeding State and Auditory Perception-Related Gene Expression

Singing by adult male zebra finches is a learned behavior important for courtship, kin recognition, and nest defense (Zann, 1996) and is inhibited by both brief periods of limited food availability and systemic injection of cannabinoids. These similar effects on singing, combined with increasing evidence for endocannabinoid involvement in feeding behavior, led us to evaluate a possible shared mechanism. We found that limited food availability both reduces singing in a cannabinoid antagonist-reversible manner and increases levels of the endocannabinoid 2-arachidonyl glycerol in various brain regions including the caudal telencephalon, an area that contains auditory telencephalon including the L2 subfield of L (L2) and caudal medial nidopallium (NCM). Development and use of an anti-zebra finch cannabinoid receptor type 1 (CB1) antibody demonstrates distinct, dense cannabinoid receptor expression within song regions including Area X, lMAN (lateral magnocellular nucleus of anterior nidopallium), HVC, RA (robust nucleus of arcopallium), and L2. NCM receives L2 projections and is implicated in integration of auditory information. Activity in this area, determined through expression of the transcription factor ZENK, is increased after exposure to unfamiliar song. Because previous work has shown that these novel song-stimulated increases in NCM activity are mitigated by cannabinoid exposure, we tested and found that similar effects on ZENK expression are produced by limiting food. Limited food-related reductions in the activity of NCM neurons were reversed by the cannabinoid antagonist SR141716A (N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide), implicating CB1 cannabinoid receptor involvement. Taken together, these experiments indicate a link between feeding state and gene expression related to auditory perception that is mediated by endocannabinoid signaling.

The integration of auditory information in the auditory cortex of the Japanese monkey

The integration of auditory information in the auditory cortex of the Japanese monkey

Integration of auditory information in the cat's visual cortex

Microelectrode recordings were made from cells in the cat's visual cortex (areas 17 and 18). Forty-six neurons (38 per cent) responded to both acoustic and visual stimuli. Many of the bimodal cells responded best to pure tones and had narrow tuning curves. Some units were excited only by hisses. For many tone-sensitive cells the acoustic receptive field was coincident with the visual receptive field. The bimodal cells occurred in anatomically distinct clusters which were separated from the purely visual cells. Because of their precise specificity these cells probably play some role in the spatial localization of auditory and visual stimuli.