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Current Opinion in Neurobiology Feb 2019Learning is essential for animal survival under changing environments. Even in its simplest form, learning involves interactions between a handful of neuronal circuits,... (Review)
Review
Learning is essential for animal survival under changing environments. Even in its simplest form, learning involves interactions between a handful of neuronal circuits, hundreds of neurons and many thousand synapses. In this review I will focus on habituation - a form of non-associative learning during which organisms decrease their response to repetitions of identical sensory stimuli. I will discuss how recent studies of the acoustic startle reflex mediated by the Mauthner cell in the zebrafish larva are helping to understand the neuroplastic processes that underlie habituation. In addition to being a fascinating biological process, habituation is clinically relevant because it is affected in various neuropsychiatric disorders in humans, including autism, schizophrenia, Fragile-X and Tourette's syndromes.
Topics: Acoustic Stimulation; Animals; Larva; Learning; Neuronal Plasticity; Reflex, Startle; Zebrafish
PubMed: 30359930
DOI: 10.1016/j.conb.2018.10.004 -
The Journal of Experimental Biology Mar 2020The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic...
The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic hearing and echolocation, e.g. the ability to downregulate their auditory sensitivity when emitting clicks. However, it remains unclear whether these adaptations also led to changes of the startle reflex. We investigated reactions to startling sounds in two bottlenose dolphins () and one false killer whale (). Animals were exposed to 50 ms, 1/3 octave band noise pulses of varying levels at frequencies of 1, 10, 25 and 32 kHz while positioned in a hoop station. Startle responses were quantified by measuring rapid muscle contractions using a three-dimensional accelerometer attached to the dolphin. Startle magnitude increased exponentially with increasing received levels. Startle thresholds were frequency dependent and ranged from 131 dB at 32 kHz to 153 dB at 1 kHz (re. 1 µPa). Startle thresholds only exceeded masked auditory AEP thresholds of the animals by 47 dB but were ∼82 dB above published behavioural audiograms for these species. We also tested the effect of stimulus rise time on startle magnitude using a broadband noise pulse. Startle responses decreased with increasing rise times from 2 to 100 ms. Models suggested that rise times of 141-220 ms were necessary to completely mitigate startle responses. Our data showed that the startle reflex is conserved in odontocetes and follows similar principles as in terrestrial mammals. These principles should be considered when assessing and mitigating the effects of anthropogenic noise on marine mammals.
Topics: Acoustic Stimulation; Animals; Auditory Threshold; Bottle-Nosed Dolphin; Dolphins; Echolocation; Female; Hawaii; Male; Reflex, Startle
PubMed: 32165452
DOI: 10.1242/jeb.208470 -
Psychological Research Feb 2020The current research was designed to assess possible differences in the emotional content of pleasant and unpleasant face emoji using acoustically evoked eyeblink...
The current research was designed to assess possible differences in the emotional content of pleasant and unpleasant face emoji using acoustically evoked eyeblink startle reflex response. Stimuli were selected from Emojipedia Webpage. First, we assessed these stimuli with a previous independent sample of 190 undergraduate students (46 males and 144 females) mean age of 21.43 years (SD 3.89). A principal axis method was performed using the 30 selected emoji faces, extracting two factors (15 pleasant and 15 unpleasant emoji). Second, we measured the acoustic startle reflex modulation in 53 young adult women [mean age 22.13 years (SD 4.3)] during the viewing of each of the 30 emoji emotional faces in the context of the theory of motivation and emotion proposed by Lang (1995), but considering only the valence dimension. We expected to find higher acoustically evoked startle responses when viewing unpleasant emoji and lower responses for pleasant ones, similarly to the results obtained in the studies using human faces as emotional stimulus. An ANOVA was conducted to compare acoustic startle responses associated with pleasant and unpleasant emoji. Results yielded main effects for picture valence (λ = 0.80, F(1, 50) = 12.80, p = .001, η = 0.20). Post-hoc t test analysis indicated significant differences in the startle response between unpleasant (50.95 ± 1.75) and pleasant (49.14 ± 2.49) emoji (t (52) = 3.59, p = .001), with a Cohen's d = 0.495. Viewing affective facial emoji expressions modulates the acoustic startle reflex response according to their emotional content.
Topics: Adult; Blinking; Emotions; Female; Humans; Photic Stimulation; Reflex, Startle; Social Media; Spain; Young Adult
PubMed: 29455232
DOI: 10.1007/s00426-018-0991-x -
Reviews in the Neurosciences 2008Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely... (Review)
Review
Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely valuable for the analysis of neural systems associated with fear and anxiety. Until recently, there have been few efforts to develop acoustic startle measurement in non-human primates. Here we review recent work in which whole body acoustic startle amplitude has been measured in rhesus monkeys. Initial studies revealed that the amplitude of whole body startle in monkeys, as in rodents and humans, is directly proportional to acoustic stimulus intensity and gradually habituates with repeated exposures. Presentation of a weak acoustic stimulus 25-5,000 msec before a startle stimulus reduces startle amplitude by 40-50% depending on inter-stimulus interval length (prepulse inhibition). We have also measured significant fear-potentiated startle in the presence of a visual stimulus after pairing it with an inescapable pulse of pressurized air (fear-potentiated startle). This effect was reduced by diazepam and morphine, but not by buspirone. Ibotenic acid-induced lesions of the amygdala prevented the acquisition of fear-potentiated startle but, remarkably, did not prevent the expression of fear-potentiated startle when fear conditioning was carried out prior to the lesion. Finally, we have developed an objective measure of fear inhibition in monkeys using a novel conditioned inhibition procedure identical to one used in rats and humans. Our data demonstrate that acoustic startle in non-human primates successfully bridges rodent and human research. The opportunity now emerges to link concepts developed in rodents to the more complex neuroanatomical and cognitive processes common to monkeys and humans.
Topics: Acoustic Stimulation; Amygdala; Animals; Anti-Anxiety Agents; Behavior, Animal; Fear; Humans; Inhibition, Psychological; Macaca mulatta; Photic Stimulation; Reflex, Acoustic; Reflex, Startle
PubMed: 18751523
DOI: 10.1515/revneuro.2008.19.2-3.171 -
Clinical Neurophysiology : Official... Jan 2012The origin of the startle reflex lies in the caudal brainstem; it can be elicited by an unexpected stimulus resulting in a bilateral activation of many muscles. Two... (Review)
Review
The origin of the startle reflex lies in the caudal brainstem; it can be elicited by an unexpected stimulus resulting in a bilateral activation of many muscles. Two subsequent responses can be measured during EMG recordings; after the initial motor reflex, lasting until about 150 ms, a second response can occur. The second response contains more emotional and voluntary behavioral responses. Clinically, syndromes with hyperstartling as common feature can be divided into three groups: hyperekplexia, stimulus-induced disorders, and neuropsychiatric disorders. Classification of startle syndromes within these three groups remains challenging. Generalized stiffness at birth, excessive startling and temporary generalized stiffness after being startled point towards hyperekplexia. Stimulus-induced disorders are distinguished by careful clinical and neurophysiological evaluation, including video recordings. Neuropsychiatric disorders usually have additional behavioural and psychiatric symptoms. Polymyographic EMG startle recordings exhibit an exaggeration of the initial motor startle reflex in hyperekplexia, while neuropsychiatric startle syndromes demonstrate a variable response pattern and abnormal behavioural features. Neurophysiological investigation of the startle reflex can help to further delineate between the startle syndromes and unravel the aetiology of neuropsychiatric startle disorders.
Topics: Animals; Brain Stem; Electromyography; Humans; Movement; Muscle Rigidity; Rats; Reflex, Abnormal; Reflex, Startle
PubMed: 22033030
DOI: 10.1016/j.clinph.2011.09.022 -
Supplements To Clinical Neurophysiology 2006
Review
Topics: Animals; Electric Stimulation; Humans; Medulla Oblongata; Movement; Muscle, Skeletal; Neural Pathways; Reflex, Startle; Reticular Formation
PubMed: 16623334
DOI: 10.1016/s1567-424x(09)70071-6 -
Clinical Neurophysiology : Official... Sep 2003To provide an overview of startle reflex methodologies applied to the examination of emotional and motivational states in humans and to review the findings in different... (Review)
Review
OBJECTIVE
To provide an overview of startle reflex methodologies applied to the examination of emotional and motivational states in humans and to review the findings in different forms of psychopathology.
METHODS
Pertinent articles were searched mostly via MEDLINE and PsycINFO.
RESULTS
The startle reflex is a non-invasive translational tool of research that bridges the gap between animal and human investigations. Startle is used to study fear and anxiety, affective disturbances, sensitization, motivational states, and homeostasis.
CONCLUSIONS
The startle reflex is highly sensitive to various factors that are of interest in the studies of emotional disorders and has promoted new areas of investigations in psychiatry. However, research in psychiatry is still in its infancy and most findings await replication. Future progress will benefit from the development of innovative and powerful designs tailored to investigate specific disorders.
SIGNIFICANCE
The startle reflex has utility as a research tool to examine trauma-related disorders, fear learning, drug addiction, and to contrast affective states and emotional processing across diagnostic groups, but its usefulness as a diagnostic tool is limited.
Topics: Animals; Anxiety Disorders; Emotions; Humans; MEDLINE; Motivation; Psychiatry; Psychophysiology; Reflex; Reflex, Startle; Substance-Related Disorders
PubMed: 12948786
DOI: 10.1016/s1388-2457(03)00202-5 -
Brain Research. Brain Research Reviews Nov 1995The startle reflex protects animals from blows or predatory attacks by quickly stiffening the limbs, body wall and dorsal neck in the brief time period before directed... (Review)
Review
The startle reflex protects animals from blows or predatory attacks by quickly stiffening the limbs, body wall and dorsal neck in the brief time period before directed evasive or defensive action can be performed. The acoustic startle reflex in rats and cats is mediated primarily by a small cluster of giant neurons in the ventrocaudal part of the nucleus reticularis pontis caudalis (RPC) of the reticular formation. Activation of these RPC neurons occurs 3-8 ms after the acoustic stimulus reaches the ear. Undetermined neurons of the cochlear nuclei activate RPC via weak monosynaptic and strong disynaptic connections. The strong disynaptic input occurs via neurons of the contralateral ventrolateral pons, including large neurons of the ventrolateral tegmental nucleus that integrate auditory, tactile and vestibular information. RPC giant neurons, in turn, activate hundreds of motoneurons in the brain stem and the length of the spinal cord via large reticulospinal axons near the medial longitudinal fasciculus. To hindlimb motoneurons, monosynaptic connections from the reticulospinal tract are weak, but disynaptic connections via spinal cord interneurons are stronger and show temporal facilitation, like the startle response itself.
Topics: Animals; Behavior; Behavior, Animal; Humans; Models, Neurological; Motor Neurons; Neural Pathways; Neurons; Reflex, Startle; Reticular Formation
PubMed: 8806018
DOI: 10.1016/0165-0173(96)00004-5 -
The International Journal of Eating... Mar 2019Patients with anorexia nervosa (AN) often show difficulties in the perception, expression, and regulation of emotions and a strong avoidance of aversive feelings....
OBJECTIVE
Patients with anorexia nervosa (AN) often show difficulties in the perception, expression, and regulation of emotions and a strong avoidance of aversive feelings. According to psychobiological models, dietary restraint and accompanying weight loss may serve as a maladaptive mechanism of emotion regulation by attenuating aversive emotional states in AN, thereby contributing to the maintenance of the disorder.
METHOD
Twenty-seven women with AN and 26 age-matched healthy women were shown short film-clips to elicit fear, sadness, amusement, and neutral emotional states. Eyeblink startle response was measured by electromyography in reaction to startle-eliciting acoustic stimuli presented 12 times binaurally during each film-clip.
RESULTS
As compared to healthy controls, patients with AN showed a blunted startle response to the fear- but not to the sadness-eliciting stimulus.
DISCUSSION
The findings support the assumption that underweight is associated with attenuated emotional reactivity to fear-eliciting material in AN. This is in line with the hypothesis that starvation and low body weight constitute a maladaptive mechanism of emotion regulation in AN, contributing to the maintenance of the disorder.
Topics: Adult; Anorexia Nervosa; Emotions; Female; Humans; Male; Reflex, Startle; Young Adult
PubMed: 30653688
DOI: 10.1002/eat.23022 -
Clinical Neurophysiology : Official... Jan 2012Excitability is probably the concept that fits better with the definition of the role of neurophysiology in the study of brainstem functions and circuits.... (Review)
Review
Excitability is probably the concept that fits better with the definition of the role of neurophysiology in the study of brainstem functions and circuits. Neurophysiological techniques are likely the best suited of all paraclinical tests for documenting the eventual excitability changes that may occur in certain physiological states and in many neurological disorders. The best known test of brainstem excitability is the blink reflex. While a single stimulus can already indicate the readiness of the interneuronal path and the facial motoneurons to fire, pairs of stimuli (conditioning and test) are suited to analyze the degree of excitability recovery after a single discharge. Another brainstem reflex circuit, which excitability testing can be of interest for physiological and clinical exams is the one involved in the startle reaction. The size of the responses and their habituation are the typical measures of excitability of the startle reflex circuit. Prepulse inhibition is a method to modulate both, the blink reflex and the startle reaction. It is defined as the inhibitory effect caused by a stimulus of an intensity low enough not to induce a response by itself on the response elicited by a subsequent stimulus. The circuits of the blink reflex, startle reaction and prepulse inhibition share some commonalities but they are different enough for the three techniques to provide unique, clinically relevant, information in certain conditions. The role of neurophysiology is not limited to testing those functions. It is important also for the assessment of many other circuits, such as those implicated in eye movements, vestibular reflexes, arousal, sleep, breathing, or autonomic reactions, which are not considered in this review.
Topics: Animals; Blinking; Brain Stem; Habituation, Psychophysiologic; Humans; Rats; Reflex, Startle
PubMed: 22030138
DOI: 10.1016/j.clinph.2011.04.029