Startle response

Summary

In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening stimuli, such as sudden noise or sharp movement, and is associated with negative affect. Usually the onset of the startle response is a startle reflex reaction. The startle reflex is a brainstem reflectory reaction (reflex) that serves to protect vulnerable parts, such as the back of the neck (whole-body startle) and the eyes (eyeblink) and facilitates escape from sudden stimuli. It is found across many different species, throughout all stages of life. A variety of responses may occur depending on the affected individual's emotional state, body posture, preparation for execution of a motor task, or other activities. The startle response is implicated in the formation of specific phobias. Startle reflex Neurophysiology A startle reflex can occur in the body through a combination of actions. A reflex from hearing a sudden loud noise will happen in

Official source

https://en.wikipedia.org/wiki/Startle_response

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Although cocaine abuse is up to three times more frequent among schizophrenic patients, it remains unclear why this should be the case and whether sex influences this relationship. Using a maternal immune activation model of schizophrenia, we tested whether animals at higher risk of developing a schizophrenia-like state are more prone to acquire cocaine self-administration behavior, and whether they show enhanced sensitivity to the reinforcing actions of cocaine or if they are resistant to extinction. Pregnant rats were injected with lipopolysaccharide on gestational day 15 and 16, and the offspring (both male and female) were tested in working memory (T-maze), social interaction and sensorimotor gating (prepulse inhibition of the acoustic startle response) paradigms. After performing these tests, the rats were subjected to cocaine self-administration regimes (0.5 mg/kg), assessing their dose-response and extinction. Male rats born to dams administered lipopolysaccharide showed impaired working memory but no alterations to their social interactions, and both male and female rats showed prepulse inhibition deficits. Moreover, similar patterns of cocaine self-administration acquisition, responsiveness to dose shifts and extinction curves were observed in both control and experimental rats. These results suggest that the higher prevalence of cocaine abuse among schizophrenic individuals is not due to a biological vulnerability directly associated to the disease and that other factors (social, educational, economic, familial, etc.) should be considered given the multifactorial nature of this illness. (C) 2016 Elsevier Inc. All rights reserved.

Pergamon-Elsevier Science Ltd2016

Two primes priming: Does feature integration occur before response activation?

Julianne Grainger, Michael Herzog, Frank Scharnowski, Thomas Schmidt

Responses to a target can be sped up or slowed down by a congruent or incongruent prime, respectively. Even though presentations are rapid, the prime and the target are thought to activate motor responses in strict sequence, with prime activation preceding target activation. In feature fusion, the opposite seems to be the case. For example, a vernier offset to the left is immediately followed by a vernier offset to the right at the same location. The two verniers are not perceived as two elements in sequence but as a single, aligned vernier. Here, we ask the question as to how features are integrated: before or after motor activation? We presented two vernier primes with opposite offset directions preceding a single vernier target. No priming effect occurred when the vernier primes were presented at the same location, indicating that verniers integrate before motor activation. There was also no priming effect when the primes were presented simultaneously at different locations, indicating that there is an integration stage different from the perceptual fusion stage. When the second prime is delayed, it determines priming, even for very long delays. To explain these long integration times, we argue that there is a buffer preceding motor activation.

Association for Research in Vision and Ophthalmology2013

Vestibular Processing and its Cortical Signature in Humans

Steven Gale

The vestibular system encodes rotations and translations of the head in space. While much is known about cortical processing of the classical Aristotelian sensory modalities, such as vision and touch, knowledge of how vestibular stimulation is encoded in the human brain is lacking, probably due to the inherent technical difficulties of recording human brain function while providing natural vestibular stimulation. Here, I used electroencephalography (EEG), psychophysics, and a custom-built rotating chair to elucidate how natural vestibular stimulation is encoded and processed in the brain, and identified novel markers of vestibular processing in the brain in the frequency domain. Specifically, in one set of experiments the spectral response to rotations were analyzed during constant velocity stimulation and short, transient stimulations in healthy subjects and bilateral vestibular-loss patients (BVPs). In another set of experiments the time course of spectral modulations was compared to that of the vestibulo-ocular response (VOR), which decays exponentially during constant velocity rotational stimulation with a time constant of 10-30s. Throughout all EEG experiments, spectral power in the alpha (8-13 Hz) band was found to consistently encode vestibular stimulation. Furthermore, the multisensory nature of the vestibular system was studied statistically by using a Bayes-optimal integration model to better understand how visual and vestibular information are combined in the brain to form a percept. Results across these experiments indicate that visual and vestibular information are not just integrated optimally, but also âfusedâ at the perceptual level.

EPFL2015