Sensory gating

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Sensory gating describes neural processes of filtering out redundant or irrelevant stimuli from all possible environmental stimuli reaching the brain. Also referred to as gating or filtering, sensory gating prevents an overload of information in the higher cortical centers of the brain. Sensory gating can also occur in different forms through changes in both perception and sensation, affected by various factors such as "arousal, recent stimulus exposure, and selective attention." [1]

Contents

Although sensory gating is largely automatic, it also occurs within the context of attention processing as the brain selectively seeks for goal-relevant information. [2] Previous studies have shown a correlation between sensory gating and different cognitive functions, but there is not yet a solid evidence implying that the relationship between sensory gating and cognitive functions are modality-independent.

Cocktail party effect

The cocktail party effect illustrates how the brain inhibits input from environmental stimuli, while still processing sensory input from the attended stimulus. The cocktail party effect demonstrates sensory gating in hearing, but the other senses also go through the same process protecting primary cortical areas from being overwhelmed.

Neural regions involved

Information from sensory receptors make their way to the brain through neurons and synapse at the thalamus. The pulvinar nuclei of the thalamus plays a major role in attention, and has a major role in filtering out unnecessary information in regards to sensory gating. In a proven clinical study, it has been found out that the two stimuli (S1 and S2) are transported within 500ms between the clicks and 8 seconds between the pairs, in which S1 is known to generate a trace of memory that lingers presumably in the hippocampal region while the S2 the arrives later to be compared with the first stimuli as it gets inhibited if provided with no new information. (Both S1 and S2 are commonly referred to auditory stimuli caused by the machines used to test sensory gating.) The pulvinar nuclei in the thalamus function as the gatekeeper, deciding which information should be inhibited, and which should be sent to further cortical areas. [3] The CNS (Central Nervous System), after the pulvinar nuclei deems the information to be irrelevant, acts as an essential inhibitory mechanism that prevents the information from flowing into higher cortical centers.

Sensory gating is mediated by a network in the brain which involves the auditory cortex (AC), prefrontal cortex, hippocampus, as well as the olfactory cortex, which plays a part in sensory gating phenomenon. Other areas of the brain associated with sensory gating include the amygdala, striatum, medial prefrontal cortex, and mid-brain dopamine cell region (GABAergic neurons only). Research on sensory gating has been primarily occurring in cortical areas where the stimulus is consciously identified because it is a less invasive means of studying sensory gating. Studies on rats also show the brain stem, thalamus, and primary auditory cortex play a role in sensory gating for auditory stimuli. [4]

Techniques for measurement

Paired-click paradigm

The paired-click paradigm is a common non-invasive technique used to measure sensory gating, a type of event-related potential. For normal sensory gating, if a person hears a pair of clicks within 500 ms of one another, the person will gate out the second click because it is perceived as being redundant. Evidence of the gating can be seen in the P50 wave, occurring in the brain 50 ms after the click. Low values of the P50 wave indicate that sensory gating has occurred. High values of the P50 wave indicate a lack of sensory gating. Individuals with schizophrenia only reduce the amplitude of S2 by 10–20%, whereas individuals without schizophrenia reduce the amplitude of S2 by 80–90%.

A subject wearing an electroencephalography cap, a conventional technique for measuring one's reactivity using sensory gating. Electroencephalography (EEG) - FET09 Prague.jpg
A subject wearing an electroencephalography cap, a conventional technique for measuring one's reactivity using sensory gating.

Other techniques

Electroencephalography (EEG) and magnetoencephalographies (MEG) are used to measure brain responses and are common techniques for studying sensory gating. One type of EEG measure used for sensory gating research is the event-related potential (ERP). EEG research on sensory gating shows that gating starts almost immediately after receiving a stimulus. Positron emission tomography (PET) studies have shown that an increased need to gate information is accompanied by increased engagement of the thalamus. P50 wave testing is one of many auditory event-related potential studies.

Sensory gating deficits and mental illness

Schizophrenia

A large interest in sensory gating research is directed at improving deficits among people diagnosed with schizophrenia. People with schizophrenia often have deficits in gating the neuronal response of the P50 wave, which is why P50 is the most widespread method of diagnosis. The test is conducted through having the patients hear two uniform sounds with an interval of 500 milliseconds. While the patients are hearing the sound, an EEG cap is used to measure the brain activity in response to those sounds. A normal subject shows a decrease in brain activity while hearing a second sound, while a subject showing equal brain activity to the first sound is more likely to have schizophrenia. Since people with schizophrenia can often have an overload of attended stimuli, the P50 wave may serve a critical role in illuminating sensory gating at a neurological level. [5]

Currently the test has been conducted on mice, and results have been identical to human subjects in that brain activity has decreased on the second sound. In the second experiment, scientists placed internal electrodes in the auditory regions of the brain. It was found that by the time the second sound occurred, a drop in brain activity had already initiated from the brainstem. The discovery of the filter effect activating as soon as the brainstem perceives a sound was carried out on mice with the "22q11 deletion syndrome," a syndrome associated with schizophrenia in humans. [5] The continuing study, to be verified, suggests that the filter system is indeed in the brainstem, offering hope for finding the neurological source of schizophrenia.

Post-Traumatic Stress Disorder (PTSD)

Those with PTSD also exhibit impaired sensory gating. Compared to those with Generalized Anxiety Disorder and control groups, those with PTSD show high sensory hyperactivity and impaired sensory disinhibition. [6] Studies on the effect of PTSD on P50 gating have produced mixed results, with some finding a similar pattern to schizophrenia, [7] some finding it was limited to auditory stimulation only, [8] and others finding no effect. [9] Impaired gating of N100 and P200 has also been observed. [9]

Drug influences

Nicotine

One reason people report they like smoking cigarettes is nicotine's ability to aid their selective attention. [3] The nicotine causes the receptors to release nitric oxide, which slows sensory inhibition causing a suppression of a subsequent stimuli. Due to its effect, nicotine can correct sensory gating deficits for individuals with schizophrenia (80% of individuals with schizophrenia smoke up to 30 cigarettes/day), [3] although the effects only last about 30 minutes since the nicotine receptors desensitize quickly. The same self-medication is present among those with attention deficit hyperactivity disorder (ADHD) as well as those on the autism spectrum.[ citation needed ]

Sensory gating and creativity

Some research shows evidence of a connection between sensory gating and creative thinking. One experiment conducted in 2015 suggests that so-called “leaky” attention spans in people with high levels of psychopathology may lead to increased creativity. During the study, the researchers discovered that creative people tend to show reduced sensory gating, filtering out sound less than the normal subjects. Reduced ability to inhibit secondary information caused a wider range of unfiltered stimuli to come through a conscious brain, enabling a creative person to integrate different ideas, rendering creative thinking. The experiment was carried out by 97 participants, whose creativity was measured through recording their achievements and conducting a divergent thinking test. After, sensory gating was measured through both the EEG and auditory clicks. The results proved that people with creative achievements did indeed show a reduced latent inhibition compared to the average subjects. Thus, the study showed evidence of a correlation between creativity and sensory gating with reduced filtering proving to be a mechanism for receiving larger range of stimuli leading to more creativity. [10]

Related Research Articles

An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light flash or a pure tone. Different types of potentials result from stimuli of different modalities and types. Evoked potential is distinct from spontaneous potentials as detected by electroencephalography (EEG), electromyography (EMG), or other electrophysiologic recording method. Such potentials are useful for electrodiagnosis and monitoring that include detections of disease and drug-related sensory dysfunction and intraoperative monitoring of sensory pathway integrity.

<span class="mw-page-title-main">Claustrum</span> Structure in the brain

The claustrum is a thin sheet of neurons and supporting glial cells, that connects to the cerebral cortex and subcortical regions including the amygdala, hippocampus and thalamus of the brain. It is located between the insular cortex laterally and the putamen medially, encased by the extreme and external capsules respectively. Blood to the claustrum is supplied by the middle cerebral artery. It is considered to be the most densely connected structure in the brain, and thus hypothesized to allow for the integration of various cortical inputs such as vision, sound and touch, into one experience. Other hypotheses suggest that the claustrum plays a role in salience processing, to direct attention towards the most behaviorally relevant stimuli amongst the background noise. The claustrum is difficult to study given the limited number of individuals with claustral lesions and the poor resolution of neuroimaging.

<span class="mw-page-title-main">Auditory cortex</span> Part of the temporal lobe of the brain

The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to language switching. It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans, curving down and onto the medial surface, on the superior temporal plane, within the lateral sulcus and comprising parts of the transverse temporal gyri, and the superior temporal gyrus, including the planum polare and planum temporale.

<span class="mw-page-title-main">Reticular formation</span> Spinal trigeminal nucleus

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. The reticular formation includes ascending pathways to the cortex in the ascending reticular activating system (ARAS) and descending pathways to the spinal cord via the reticulospinal tracts.

A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 25 and 140 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.

<span class="mw-page-title-main">K-complex</span>

A K-complex is a waveform that may be seen on an electroencephalogram (EEG). It occurs during stage 2 NREM sleep. It is the "largest event in healthy human EEG". They are more frequent in the first sleep cycles.

Sensory overload occurs when one or more of the body's senses experiences over-stimulation from the environment.

<span class="mw-page-title-main">Thalamocortical radiations</span> Neural pathways between the thalamus and cerebral cortex

In neuroanatomy, thalamocortical radiations also known as thalamocortical fibres, are the efferent fibres that project from the thalamus to distinct areas of the cerebral cortex. They form fibre bundles that emerge from the lateral surface of the thalamus.

The mismatch negativity (MMN) or mismatch field (MMF) is a component of the event-related potential (ERP) to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but has most frequently been studied for hearing and for vision, in which case it is abbreviated to vMMN. The (v)MMN occurs after an infrequent change in a repetitive sequence of stimuli For example, a rare deviant (d) stimulus can be interspersed among a series of frequent standard (s) stimuli. In hearing, a deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, loudness, or location. The MMN can be elicited regardless of whether someone is paying attention to the sequence. During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN. In the case of visual stimuli, the MMN occurs after an infrequent change in a repetitive sequence of images.

A topographic map is the ordered projection of a sensory surface, like the retina or the skin, or an effector system, like the musculature, to one or more structures of the central nervous system. Topographic maps can be found in all sensory systems and in many motor systems.

<span class="mw-page-title-main">Synaptic gating</span>

Synaptic gating is the ability of neural circuits to gate inputs by either suppressing or facilitating specific synaptic activity. Selective inhibition of certain synapses has been studied thoroughly, and recent studies have supported the existence of permissively gated synaptic transmission. In general, synaptic gating involves a mechanism of central control over neuronal output. It includes a sort of gatekeeper neuron, which has the ability to influence transmission of information to selected targets independently of the parts of the synapse upon which it exerts its action.

Echoic memory is the sensory memory that registers specific to auditory information (sounds). Once an auditory stimulus is heard, it is stored in memory so that it can be processed and understood. Unlike most visual memory, where a person can choose how long to view the stimulus and can reassess it repeatedly, auditory stimuli are usually transient and cannot be reassessed. Since echoic memories are heard once, they are stored for slightly longer periods of time than iconic memories. Auditory stimuli are received by the ear one at a time before they can be processed and understood.

Recurrent thalamo-cortical resonance is an observed phenomenon of oscillatory neural activity between the thalamus and various cortical regions of the brain. It is proposed by Rodolfo Llinas and others as a theory for the integration of sensory information into the whole of perception in the brain. Thalamocortical oscillation is proposed to be a mechanism of synchronization between different cortical regions of the brain, a process known as temporal binding. This is possible through the existence of thalamocortical networks, groupings of thalamic and cortical cells that exhibit oscillatory properties.

In neuroscience, the N100 or N1 is a large, negative-going evoked potential measured by electroencephalography ; it peaks in adults between 80 and 120 milliseconds after the onset of a stimulus, and is distributed mostly over the fronto-central region of the scalp. It is elicited by any unpredictable stimulus in the absence of task demands. It is often referred to with the following P200 evoked potential as the "N100-P200" or "N1-P2" complex. While most research focuses on auditory stimuli, the N100 also occurs for visual, olfactory, heat, pain, balance, respiration blocking, and somatosensory stimuli.

Audio-visual entrainment (AVE), a subset of brainwave entrainment, uses flashes of lights and pulses of tones to guide the brain into various states of brainwave activity. AVE devices are often termed light and sound machines or mind machines. Altering brainwave activity is believed to aid in the treatment of psychological and physiological disorders.

The oddball paradigm is an experimental design used within psychology research. Presentations of sequences of repetitive stimuli are infrequently interrupted by a deviant stimulus. The reaction of the participant to this "oddball" stimulus is recorded.

Pre-attentive processing is the subconscious accumulation of information from the environment. All available information is pre-attentively processed. Then, the brain filters and processes what is important. Information that has the highest salience or relevance to what a person is thinking about is selected for further and more complete analysis by conscious (attentive) processing. Understanding how pre-attentive processing works is useful in advertising, in education, and for prediction of cognitive ability.

Selective auditory attention, or selective hearing, is a process of the auditory system where an individual selects or focuses on certain stimuli for auditory information processing while other stimuli are disregarded. This selection is very important as the processing and memory capabilities for humans has a limited capacity. When people use selective hearing, noise from the surrounding environment is heard by the auditory system but only certain parts of the auditory information are chosen to be processed by the brain.

In electroencephalography, the P50 is an event related potential occurring approximately 50 ms after the presentation of a stimulus, usually an auditory click. The P50 response is used to measure sensory gating, or the reduced neurophysiological response to redundant stimuli.

<span class="mw-page-title-main">Auditosensory cortex</span>

Auditosensory cortex is the part of the auditory system that is associated with the sense of hearing in humans. It occupies the bilateral primary auditory cortex in the temporal lobe of the mammalian brain. The term is used to describe Brodmann area 42 together with the transverse temporal gyri of Heschl. The auditosensory cortex takes part in the reception and processing of auditory nerve impulses, which passes sound information from the thalamus to the brain. Abnormalities in this region are responsible for many disorders in auditory abilities, such as congenital deafness, true cortical deafness, primary progressive aphasia and auditory hallucination.

References

  1. ↑ D.A. Wilson, in The Senses: A Comprehensive Reference, 2008
  2. ↑ Jones, L.A.; Hills, P.J.; Dick, K.M.; Jones, S.P.; Bright, P. (February 2016). "Cognitive mechanisms associated with auditory sensory gating". Brain and Cognition. 102: 33–45. doi:10.1016/j.bandc.2015.12.005. ISSN   0278-2626. PMC   4727785 . PMID   26716891.
  3. 1 2 3 Cromwell, Howard C.; Mears, Ryan P.; Wan, Li; Boutros, Nash N. (April 2008). "Sensory Gating: A Translational Effort From Basic to Clinical Science". Clinical EEG and Neuroscience. 39 (2): 69–72. doi:10.1177/155005940803900209. ISSN   1550-0594. PMC   4127047 . PMID   18450171.
  4. ↑ Cheng, Chia-Hsiung; Chan, Pei-Ying S.; Niddam, David M.; Tsai, Shang-Yueh; Hsu, Shih-Chieh; Liu, Chia-Yih (2016-02-04). "Sensory gating, inhibition control and gamma oscillations in the human somatosensory cortex". Scientific Reports. 6 (1): 20437. Bibcode:2016NatSR...620437C. doi: 10.1038/srep20437 . ISSN   2045-2322. PMC   4740805 . PMID   26843358.
  5. 1 2 Kim, Stefani (2019-09-09). "Researchers Study Mechanism behind Auditory Sensory Gating -..." Hearing Review. Retrieved 2020-06-22.
  6. ↑ Clancy, Kevin; Ding, Mingzhou; Bernat, Edward; Schmidt, Norman B.; Li, Wen (2017-07-01). "Restless 'rest': intrinsic sensory hyperactivity and disinhibition in post-traumatic stress disorder". Brain. 140 (7): 2041–2050. doi: 10.1093/brain/awx116 . ISSN   0006-8950. PMC   6059177 . PMID   28582479.
  7. ↑ Ghisolfi, Eduardo S.; Margis, Regina; Becker, Jefferson; Zanardo, Ana Paula; Strimitzer, Ivo M.; Lara, Diogo R. (2004-02-01). "Impaired P50 sensory gating in post-traumatic stress disorder secondary to urban violence". International Journal of Psychophysiology. 51 (3): 209–214. doi:10.1016/j.ijpsycho.2003.09.002. ISSN   0167-8760. PMID   14962572.
  8. ↑ Neylan, Thomas C.; Fletcher, Daniel J.; Lenoci, Maryann; McCallin, Keith; Weiss, Daniel S.; Schoenfeld, Frank B.; Marmar, Charles R.; Fein, George (1999-12-15). "Sensory gating in chronic posttraumatic stress disorder: reduced auditory p50 suppression in combat veterans". Biological Psychiatry. 46 (12): 1656–1664. doi:10.1016/S0006-3223(99)00047-5. ISSN   0006-3223. PMID   10624547. S2CID   5011944.
  9. 1 2 Meteran, Hanieh; Vindbjerg, Erik; Uldall, Sigurd Wiingaard; Glenthøj, Birte; Carlsson, Jessica; Oranje, Bob (March 2019). "Startle habituation, sensory, and sensorimotor gating in trauma-affected refugees with posttraumatic stress disorder". Psychological Medicine. 49 (4): 581–589. doi: 10.1017/S003329171800123X . ISSN   0033-2917. PMID   29769152.
  10. ↑ "Creativity and Sensory Gating". Psychology Today. Retrieved 2020-06-22.
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