Startle Reflex

EMG responses elicited by sudden onset of free fall and a startling auditory stimulus were investigated in healthy subjects while lying on a couch with their eyes closed. Muscle responses were recorded from masseter (V cranial nerve), orbicularis oculi and mentalis (VII nerve) and sternomastoid and trapezoid (XI nerve). A similar sequence of muscle activation and absolute latencies occurred in response to both stimulus modalities, consisting of a blink (30 msec) followed simultaneously by mentalis, sternomastoid and trapezoid (55 msec). Masseter could either be simultaneously activated with the latter muscles or follow after a delay of 10-20 msec. A patient with bilateral cochleo-vestibular nerve section had responses at comparable latencies in the free fall experiment. The similarities between the reaction to free fall and a startling auditory stimulus indicate that the early response to free fall constitutes a startle and that various stimuli converge onto a common response genera...

For the purpose of studying the potential neurobehavioral effects of different human apolipoprotein E (apoE) isoforms produced within the brain, transgenic (TG) mice were generated in which human apoE3 or apoE4 isoforms were under control of an astrocyte-specific, glial fibrillary acidic protein promoter and these TG mice were bred back to apoE knockout (KO) mice. Behavioral phenotypes of apoE3 and apoE4 TG mice were derived by conducting a longitudinal study in which apoE3 and apoE4 TG mice were compared with apoE KO and wild-type (WT) mice (all male) on several behavioral measures. Analysis of locomotor activity, "open-field" behaviors, acoustic startle/prepulse inhibition, and elevated plus maze data suggested that the apoE TG/KO groups were more "emotionally reactive" than WT mice, with apoE4 mice typically being the most reactive. The absence of performance differences among groups on the rotating holeboard and water navigation tasks suggested intact reference memory processing in apoE TG/KO mice. However, apoE4 mice were profoundly impaired on a working memory-based protocol in the radial arm maze (11-14 months). Nonassociative factors (sensorimotor capacities or emotionality differences) did not appear to confound interpretation of the learning/memory results. Western blot analysis revealed no alterations in the level of synaptic, neuronal, or glial markers in neocortex or hippocampus and histologic analysis revealed no evidence of Abeta deposition or neuritic plaques in the apoE KO/TG mice. Our findings suggest that apoE4 expression in the brain may have selective deleterious effects on memory function in the absence of typical Alzheimer's-like neuropathology.

Rationale  Mescaline is a nonselective serotonin receptor agonist. It has relatively delayed onset of action and prolonged duration. Mescaline attenuates various behavioral parameters in rats; however, no information is available about its pharmacokinetics in rats and its relation to the behavioral changes produced by the drug. Objectives  The present study evaluates the spontaneous locomotor activity and sensorimotor gating in relation to mescaline

ADHD is characterized by inattention, hyperactivity, and disinhibition, including the inability to screen out distracting stimuli. Prepulse inhibition (PPI) of startle indexes a related gating process and is enhanced during attended compared to ignored stimuli. We predicted that PPI during attended stimuli would be enhanced by the stimulant methylphenidate (MPH) and that this effect would be moderated by baseline PPI. Children with ADHD (n=36) completed a baseline day and a randomized, double-blind medication trial (placebo vs. sustained release MPH). Bilateral startle eyeblink EMG was measured during a tone discrimination task. MPH enhanced PPI during attended, but not during ignored stimuli. Extending findings that pretreatment functioning moderates stimulant effects on PPI, this effect tended to be inversely related to baseline PPI. These data fit with the clinical literature on ADHD and the hypothesis that MPH enhances interference control for important environmental stimuli.

We examined the moderating influence of dispositional behavioral inhibition system (BIS) and behavioral activation system (BAS) sensitivities on the relationship of startling background music with emotion-related subjective and physiological responses elicited during reading news reports, and with memory performance among 26 adult men and women. Physiological parameters measured were respiratory sinus arrhythmia (RSA), electrodermal activity (EDA), and facial electromyography (EMG). The results showed that, among high BAS individuals, news stories with startling background music were rated as more interesting and elicited higher zygomatic EMG activity and RSA than news stories with non-startling music. Among low BAS individuals, news stories with startling background music were rated as less pleasant and more arousing and prompted higher EDA. No BIS-related effects or effects on memory were found. Startling background music may have adverse (e.g., negative arousal) or beneficial effects (e.g., a positive emotional state and stronger positive engagement) depending on dispositional BAS sensitivity of an individual. Actual or potential applications of this research include the personalization of media presentations when using modern media and communications technologies.

We argue that the stimuli used in traditional fear conditioning paradigms are too simple to model the learning and unlearning of complex fear memories. We therefore developed and tested an adapted fear conditioning paradigm, specifically designed for the study of complex associative memories. Second, we explored whether manipulating the meaning and complexity of the CS-UCS association strengthened the learned fear association. In a two-day differential fear conditioning study, participants were randomly assigned to two experimental conditions. All participants were subjected to the same CSs (i.e., pictures) and UCS (i.e., 3 s film clip) during fear conditioning. However, in one of the conditions (negative-relevant context), the reinforced CS and UCS were meaningfully connected to each other by a 12 min aversive film clip presented prior to fear acquisition. Participants in the other condition (neutral context) were not able to make such meaningful connection between these stimuli, a...

Translational biomarkers, such as prepulse inhibition (PPI) of the acoustic startle response, are playing an increasingly important role in the development of antipsychotic drugs for schizophrenia and related conditions. However, attempts to reliably induce a PPI deficit by psychotomimetic drugs have not been successful, leaving an unmet need for a cross-species psychosis model sensitive to this widely studied surrogate treatment target. Sleep deprivation (SD) might be such a model as it has previously been shown to induce PPI deficits in rats, which could be selectively prevented with antipsychotic but not anxiolytic or antidepressant compounds. Here, in a first proof-of-concept study we tested whether SD induces a deficit in PPI and an increase in psychosis-like symptoms in healthy humans. In two counterbalanced sessions, acoustic PPI and self-reported psychosis-like symptoms (Psychotomimetic States Inventory) were measured in 24 healthy human volunteers after a normal night's...

In common parlance, the effect of the cinematic startle is typically referred to as a “jump scare.” As the name suggests, a jump scare represents that moment in a horror or suspense-thriller film when the audience is systematically jolted by an unexpected (or sometimes expected) fright. Many critics regard the startle and its associated jump scare as cheap and heavy-handed, seemingly ignoring the practice of repeat viewings for which the persistent startle effect seems most suited, which could have implications for those interested in cases of anomalous suspense first suggested by Gerrig (1996). The cinematic startle is an enormously powerful effect and understanding how timing and highly focused attention play a role in generating that effect is crucial to understanding these films’ appeal. Through an analysis of paranormal horror films including Paranormal Activity (Peli, 2007), Insidious (Wan, 2010), The Conjuring (Wan, 2013), and their associated sequels, I re-examine the contemporary jump scare as a uniquely cinematic and well-crafted effect.

Light & Scent (People Relearn a Heightened Sense of Smell to Enhance Brain Plasticity)

We're born smellers.  Being enveloped in "womb-waters" means our smell sense is not fully-activated with the mechanisms for breathing air (replete with essential scent molecules) until we take that very first lung-filling breath.  In fact, the human olfactory system is increasingly understood to be highly dynamic. The neurobiological underpinnings of this plasticity, including “bottom-up” factors like regulation of peripheral odor receptors and “top-down” factors like the sensory consequences of emotional and cognitive states, are  really just beginning to be explored with regards to more therapeutic potentials. As the human olfactory bulb is actually quite large in absolute terms and contains a similar number of neurons to that of other mammals there's increasing awareness of engaging our excellent olfactory abilities to assist in trauma and rehabilitative recovery.  (Check out some recent discoveries about this topic to learn how and why we can detect and discriminate an extraordinary range of odors.)

~ http://www.natureandforesttherapy.org/blog/on-the-scent-of-wellness

​~ http://www.npr.org/sections/health-shots/2017/06/06/531744473/learn-to-sniff-the-world-like-a-dog-does-and-see-in-a-new-way​

~​Poor human olfaction is a 19th-century myth​
http://science.sciencemag.org/content/356/6338/eaam7263

In our mother, the foods she ingested and air she breathed, while being filtered, prepared us to emerge ready and able to smell:  with the mighty task @ hand -- singularly feeding.  We, alone, released from the umbilical, needed to seek out mother's nipple.  Scent being our pathfinder.  Though, in these earliest of "sniffings" we're also unleashing a slew of early and rapid neurological changes to bring the nose, eyes and even ears into a whole concerted/highly orchestrated neurological realm of learning, forever changing how we navigate and discover the essence of our brand new world.

Startle reflex is something everyone knows about.  We've all felt it at one time or another.  It is the response of our mind and our body from a sudden unexpected stimulus. When startled, our bodies go through many physical changes including contraction of muscles of the arm and leg, blinking, increase in blood pressure, respiration and breathing rate. While the muscle contraction responses generally resolve themselves in a matter of seconds, it often takes our breathing, respiration and blood pressure much more time to normalize.  In humans, this is typically measured by determining the magnitude of the muscle activity of the ​ eyeblink reflex​ during the emission of a sudden loud noise. (And this response is capitalized on in certain " eye-movement-based " PTS therapy approaches such as Eye-Movement Desensitization and Reprocessing (EMDR), Comprehensive Resource Model (CRM) and Accelerated Resolution Therapy (ART)).

Abstract Rationale. Ayahuasca, a South American psychotropic plant tea, combines the psychedelic agent and 5-HT2A/2C agonist N,N-dimethyltryptamine (DMT) with β-carboline alkaloids showing monoamine oxidase-inhibiting properties. Current human research with psychedelics and entactogens has explored the possibility that drugs displaying agonist activity at the 5-HT2A/2C sites temporally disrupt inhibitory neural mechanisms thought to intervene in the normal filtering of information. Suppression of the P50 auditory evoked potential (AEP) and prepulse inhibition of startle (PPI) are considered operational measures of sensory (P50 suppression) and sensorimotor (PPI) gating. Contrary to findings in lower animals, unexpected increases in sensorimotor gating have been found in humans following the administration of the serotonergic psychedelic psilocybin and the serotonin releaser 3,4-methylenedioxymethamphetamine (MDMA). In addition, to our knowledge P50 suppression has not been assessed previously in humans following the administration of a 5-HT2A/2C agonist. Objectives. To assess the effects of the acute administration of ayahuasca on P50 suppression and PPI in humans, in order to evaluate the drug's modulatory actions on these measures of sensory and sensorimotor gating. Methods. Eighteen healthy volunteers with prior experience of psychedelic drug use participated in a clinical trial in which placebo or ayahuasca doses (0.6 mg and 0.85 mg DMT/kg body weight) were administered according to a double-blind, cross-over balanced design. P50 and startle reflex (pulse-alone and 60 ms, 120 ms, 240 ms and 2000 ms prepulse-to-pulse intervals) recordings were undertaken at 1.5 h and 2 h after drug intake, respectively. Results. Ayahuasca produced diverging effects on each of the two gating measures evaluated. Whereas significant dose-dependent reductions of P50 suppression were observed after ayahuasca, no significant effects were found on the startle response, its habituation rate, or on PPI at any of the prepulse-to-pulse intervals studied. Conclusion. The present findings indicate, at the doses tested, a decremental effect of ayahuasca on sensory gating, as measured by P50 suppression, and no distinct effects on sensorimotor gating, as measured by PPI.