Quantifying the Speed of Chromatophore Activity at the Single-Organ Level in Response to a Visual Startle Stimulus in Living, Intact Squid

The speed of adaptive body patterning in coleoid cephalopods is unmatched in the natural world. While the literature frequently reports their remarkable ability to change coloration significantly faster than other species, there is limited research on the temporal dynamics of rapid chromatophore coordination underlying body patterning in living, intact animals. In this exploratory pilot study, we aimed to measure chromatophore activity in response to a light flash stimulus in seven squid, Doryteuthis pealeii. We video-recorded the head/arms, mantle, and fin when squid were presented with a light flash startle stimulus. Individual chromatophores were detected and tracked over time using image analysis. We assessed baseline and response chromatophore surface area parameters before and after flash stimulation, respectively. Using change-point analysis, we identified 4,065 chromatophores from 185 trials with significant surface area changes elicited by the flash stimulus. We defined the temporal dynamics of chromatophore activity to flash stimulation as the latency, duration, and magnitude of surface area changes (expansion or retraction) following the flash presentation. Post stimulation, the response’s mean latency was at 50 ms (± 16.67 ms), for expansion and retraction, across all body regions. The response duration ranged from 217 ms (fin, retraction) to 384 ms (heads/arms, expansion). While chromatophore expansions had a mean surface area increase of 155.06%, the retractions only caused a mean reduction of 40.46%. Collectively, the methods and results described contribute to our understanding of how cephalopods can employ thousands of chromatophore organs in milliseconds to achieve rapid, dynamic body patterning.

Neuronal subset-specific Pten-deficient mice do not exhibit deficits in sensorimotor gating processes

Background: Deficits in sensorimotor gating have been reported in individuals with autism spectrum disorder (ASD), as well as in ASD murine models. However, this behavior has not been examined in the neuronal subset-specific (NS)-Pten knockout (KO) model of ASD. NS-Pten KO mice exhibit hyperactivity of the PI3K/AKT/mTOR signaling pathway which is implicated in the onset of autistic deficits. This study investigates the potential relationship between PI3K/AKT/mTOR signaling and deficits in sensorimotor gating. Methods: To assess sensorimotor gating in NS-Pten KO mice we utilized a three-day paradigm. On day 1 (habituation) the mice were administered 80 repetitions of a 120-dB startle stimulus. On day 2, prepulse inhibition was measured with 90 trials of the startle stimulus that was paired with a smaller (2, 7, or 12 dB) prepulse stimulus. Day 3 was assessed one week later, consisting of randomized startle trials and trials with no stimulus and was used to determine the startle response. Results: No significant difference between NS-Pten KO or wildtype (WT) mice was found for habituation (p > 0.05). No significant differences were found between groups when assessing the percentage of prepulse inhibition at 2, 7, and 12 dB (p > 0.05). There was also no difference in startle response between groups (p > 0.05). Conclusion: Our study found that the NS-Pten KO model does not display significant deficits in sensorimotor gating processes. The present findings help to elucidate the relationship between PI3K/AKT/mTOR hyperactivation and sensory reactivity.

Neuronal subset-specific Pten-deficient mice do not exhibit deficits in sensorimotor gating processes

Background: Deficits in sensorimotor gating have been reported in individuals with autism spectrum disorder (ASD), as well as in ASD murine models. However, this behavior has not been examined in the neuronal subset-specific (NS)-Pten knockout (KO) model of ASD. NS-Pten KO mice exhibit hyperactivity of the PI3K/AKT/mTOR signaling pathway which is implicated in the onset of autistic deficits. This study investigates the potential relationship between PI3K/AKT/mTOR signaling and deficits in sensorimotor gating. Methods: To assess sensorimotor gating in NS-Pten KO mice we utilized a three-day paradigm. On day 1 (habituation) the mice were administered 80 repetitions of a 120-dB startle stimulus. On day 2, prepulse inhibition was measured with 90 trials of the startle stimulus that was paired with a smaller (2, 7, or 12 dB) prepulse stimulus. Day 3 was assessed one week later, consisting of randomized startle trials and trials with no stimulus and was used to determine the startle threshold. Results: No significant difference between NS-Pten KO or wildtype (WT) mice was found for habituation (p > 0.05). No significant differences were found between groups when assessing the percentage of prepulse inhibition at 2, 7, and 12 dB (p > 0.05). There was also no difference in startle threshold between groups (p > 0.05). Conclusion: Our study found that the NS-Pten KO model does not display significant deficits in sensorimotor gating processes. The present findings help to elucidate the relationship between PI3K/AKT/mTOR hyperactivation and sensory reactivity.

Auditory Warnings Invoking Startle Response Cause Faster and More Intense Neck Muscle Contractions Prior to Head Impacts

High-pressure level and sudden sound, especially during an elevated state of alertness can elicit a startle response. Startle response can induce sudden, intense muscle activations. Some studies have shown that increasing neck muscle activation during impact situations can reduce the risk of concussion and neck injury. This research aimed to study muscle coactivation patterns, contraction latency and the level of muscle activation in startle response compared to the voluntary response. To achieve this goal, a testbed capable of applying impacts to the head in four directions was created. Auditory (115 dB) startle stimulus was delivered and muscle activation measured using sEMG on neck muscles during startle and voluntary responses. We investigated a 1000 ms time period starting at the time that the sound is played to the time at impact. Results indicate that the first muscle activation in startle response is 2.1 times higher, 5.9 times faster and involved more muscles than in a voluntary response.

Neuronal subset-specific Pten-deficient mice do not exhibit deficits in sensorimotor gating processes

Background: Deficits in sensorimotor gating have been reported in individuals with autism spectrum disorder (ASD), as well as in ASD murine models. However, this behavior has been rarely examined in the neuronal subset-specific (NS)-Pten knockout (KO) model of ASD. NS-Pten KO mice exhibit hyperactivity of the PI3K/AKT/mTOR signaling pathway which is implicated in the onset of autistic deficits. This study investigates the potential relationship between PI3K/AKT/mTOR signaling and deficits in sensorimotor gating. Methods: To assess sensorimotor gating in NS-Pten KO mice we utilized a three-day paradigm. On day 1 (habituation) the mice were administered 80 repetitions of a 120-dB startle stimulus. On day 2, prepulse inhibition was measured with 90 trials of the startle stimulus that was paired with a smaller (70, 75, or 80 dB) prepulse stimulus. Day 3 was assessed one week later, consisting of randomized startle trials and trials with no stimulus and was used to determine the startle threshold. Results: No significant difference between NS-Pten KO or wildtype (WT) mice was found for habituation (p > 0.05). No significant differences were found between groups when assessing the percentage of prepulse inhibition at 70, 75, and 80 dB (p > 0.05). There was also no difference in startle threshold between groups (p > 0.05). Conclusion: Our study found that the NS-Pten KO model does not display significant deficits in sensorimotor gating processes. The present findings help to elucidate the relationship between PI3K/AKT/mTOR hyperactivation and sensory reactivity.

Effects of elevated CO2on predator avoidance behaviour by reef fishes is not altered by experimental test water

Pioneering studies into the effects of elevated CO2on the behaviour of reef fishes often tested high-CO2reared fish using control water in the test arena. While subsequent studies using rearing treatment water (control or high CO2) in the test arena have confirmed the effects of high CO2on a range of reef fish behaviours, a further investigation into the use of different test water in the experimental arena is warranted. Here, we used a fully factorial design to test the effect of rearing treatment water (control or high CO2) and experimental test water (control or high CO2) on antipredator responses of larval reef fishes. We tested antipredator behaviour in larval clownfishAmphiprion perculaand ambon damselfishPomacentrus amboinensis, two species that have been used in previous high CO2 experiments. Specifically, we tested if: (1) using control or high CO2water in a two channel flume influenced the response of larval clownfish to predator odour; and (2) using control or high CO2water in the test arena influenced the escape response of larval damselfish to a startle stimulus. Finally, (3) because the effects of high CO2on fish behaviour appear to be caused by altered function of the GABA-A neurotransmitter we tested if antipredator behaviours were restored in clownfish treated with a GABA antagonist (gabazine) in high CO2water. Larval clownfish reared from hatching in control water (496 µatm) strongly avoided predator cue whereas larval clownfish reared from hatching in high CO2(1,022 µatm) were attracted to the predator cue, as has been reported in previous studies. There was no effect on fish responses of using either control or high CO2water in the flume. Larval damselfish reared for four days in high CO2(1,051 µatm) exhibited a slower response to a startle stimulus and slower escape speed compared with fish reared in control conditions (464 µatm). There was no effect of test water on escape responses. Treatment of high-CO2reared clownfish with 4 mg l−1gabazine in high CO2seawater restored the normal response to predator odour, as has been previously reported with fish tested in control water. Our results show that using control water in the experimental trials did not influence the results of previous studies on antipredator behaviour of reef fishes and also supports the results of novel experiments conducted in natural reef habitat at ambient CO2levels.

Effects of elevated CO2 on predator avoidance behaviour by reef fishes is not altered by experimental test water

Pioneering studies into the effects of elevated CO2 on the behaviour of reef fishes often tested high-CO2 reared fish using control water in the test arena. While subsequent studies using rearing treatment water (control or high CO2) in the test arena have confirmed the effects of high CO2 on a range of reef fish behaviours, a further investigation into the use of different test water in the experimental arena is warranted. Here, we used a fully factorial design to test the effect of rearing treatment water (control or high CO2) and experimental test water (control or high CO2) on antipredator responses of larval reef fishes. We tested antipredator behaviour in larval clownfish Amphiprion percula and ambon damselfish Pomacentrus amboinensis, two species that have been used in previous high CO2 experiments. Specifically we tested if: 1) using control or high CO2 water in a two channel flume influenced the response of larval clownfish to predator odour, and 2) using control or high CO2 water in the test arena influenced the escape response of larval damselfish to a startle stimulus. Finally, 3) because the effects of high CO2 on fish behaviour appear to be caused by altered function of the GABA-A neurotransmitter we tested if antipredator behaviours were restored in clownfish treated with a GABA antagonist (gabazine) in high CO2 water. Larval clownfish reared from hatching in control water (496 μatm) strongly avoided predator cue whereas larval clownfish reared from hatching in high CO2 (1022 μatm) were attracted to the predator cue, as has been reported in previous studies. There was no effect of testing fish using control or high CO2 water in the flume. Larval damselfish reared for 4 days in high CO2 (1051 μatm) exhibited a slower response to a startle stimulus, slower escape speed and a shorter escape distance compared with fish reared in control conditions (464 μatm). There was no effect of test water on escape responses. Treatment of high-CO2 reared clownfish with 4 mg l−1 gabazine in high CO2 seawater restored the normal response to predator odour, as has been previously reported with fish tested in control water. Our results show that using control water in the experimental trials did not influence the results of previous studies on antipredator behaviour of reef fishes and also supports the results of novel experiments conducted in natural reef habitat at ambient CO2 levels.

Further Evidence for the Independent Reflex-Eliciting and Reflex-Inhibiting Effects of a Startle-Blink Eliciting Stimulus

A small change in the environment (a prepulse) that just precedes a startle-eliciting stimulus can reduce the size of the elicited reflex, but a prepulse does not appear to diminish the ability of the startle-eliciting stimulus to depress a startle response elicited a little later. The reflex-eliciting and reflex-modifying effects of startle stimuli seem to be independent. However, most support for this observation rests on a failure to reject the null hypothesis, and relatively little of this research has employed the acoustic startle blink in human beings. The purpose of the present study was to provide additional evidence on this issue. Participants (n = 20) encountered trials in which a prepulse (p) and two 103 dB(A) blink-eliciting noise bursts (S1 and S2) were given in succession. The prepulse (a synchronous word and tone) occurred 150 ms prior to S1. The prepulse inhibited the startle blink to S1, and S1 depressed the blink elicited 1.5 s later by S2. However, regardless of whether p inhibited the blink to S1, S1 maintained the same capacity to depress the blink to S2. In contrast, a softer S1 (88 dB(A); S1attenuated), which produced a blink nearly matching the size of the prepulse-inhibited blink, did not significantly depress the response to S2. Participants also judged the loudness of S1 and S2. The prepulse reduced the perceived intensity of S1, but much less so than caused by reducing the actual intensity of S1, and proportionally much less so than the prepulse reduced the blink to S1. These results provide further evidence for independent reflex-eliciting and reflex-modifying effects of a startle-eliciting stimulus and argue against the notion that prepulses strongly reduce the general sensory impact of the startle stimulus.