Distortions in predicted motion: Pitch and direction influence imagined speed for a visual object during occlusion

<p>Visual motion prediction is essential for making key judgements about objects in the environment. These judgements are typically investigated using a time-to-contact (TTC) task, in which an object travels along a straight trajectory and disappears behind an occluder. Participants make a response coinciding with the moment the object would have contacted a visual landmark. The assumption is that the motion continues behind the occluder. This task is used to measure how we perceive and predict the arrival-time of objects. The addition of sound to TTC tasks generally enhances visual judgements. One characteristic which may affect how sound influences visual motion judgements is pitch. A rising pitch is associated with speeded motion and a falling pitch with slowed motion. Pitch change could therefore lead to biases in visual motion judgements; however, this has not yet been investigated. Furthermore, TTC tasks can utilise horizontal or vertical motion. In vertical motion, an additional variable that may be critical for TTC estimations is gravity. It is postulated that humans possess an internal model of gravity that allows us to make accurate predictions for downward motion. This model assumes faster downward than upward motion. However, this model can be wrongfully applied in constant speed tasks, producing faster speed estimations for downward stimuli when there is no acceleration. Therefore, vertical motion could lead to additional biases in visual motion judgements. This thesis investigated whether pitch and gravity could affect the imagined speed of an object under occlusion. Specifically, a rising pitch was hypothesised to produce speeded predicted motion and falling pitch, slowed predicted motion. I investigated the influence of pitch change in vertical and horizontal planes. I also investigated two different aspects of pitch change, since dynamic pitch is a novel addition to TTC paradigms. Experiment 1A explored gradual pitch change and Experiment 1B used sudden pitch change. The hypothesised pitch effects were observed for a gradual, but not a sudden pitch change. However, a gravity effect was observed across both Experiments 1A and 1B, suggesting the presence of sound does not moderate this effect. I also examined the cortical substrates of the audio-visual TTC task components by using transcranial magnetic stimulation (TMS) in Experiment 2. The superior temporal sulcus (STS) was targeted in this experiment, as it has been implicated in audio-visual integration. TMS causes neuronal inhibition, and as such, can be used to determine whether an area is involved in a task. If the STS is responsible for audio-visual integration in a TTC task, then TMS to the STS should disrupt the pitch effects evidenced in Experiment 1A. That is, a change in pitch should have no effect on TTC judgements compared to a constant tone. This result was evident only for rising tones, suggesting the involvement of the STS in the generating speeded predicted motion. The pitch effects observed in Experiment 1A and Experiment 2 implicate pitch in the production of biases in motion imagery for visual motion judgements, particularly for visual stimuli under occlusion.</p>

Distortions in predicted motion: Pitch and direction influence imagined speed for a visual object during occlusion

<p>Visual motion prediction is essential for making key judgements about objects in the environment. These judgements are typically investigated using a time-to-contact (TTC) task, in which an object travels along a straight trajectory and disappears behind an occluder. Participants make a response coinciding with the moment the object would have contacted a visual landmark. The assumption is that the motion continues behind the occluder. This task is used to measure how we perceive and predict the arrival-time of objects. The addition of sound to TTC tasks generally enhances visual judgements. One characteristic which may affect how sound influences visual motion judgements is pitch. A rising pitch is associated with speeded motion and a falling pitch with slowed motion. Pitch change could therefore lead to biases in visual motion judgements; however, this has not yet been investigated. Furthermore, TTC tasks can utilise horizontal or vertical motion. In vertical motion, an additional variable that may be critical for TTC estimations is gravity. It is postulated that humans possess an internal model of gravity that allows us to make accurate predictions for downward motion. This model assumes faster downward than upward motion. However, this model can be wrongfully applied in constant speed tasks, producing faster speed estimations for downward stimuli when there is no acceleration. Therefore, vertical motion could lead to additional biases in visual motion judgements. This thesis investigated whether pitch and gravity could affect the imagined speed of an object under occlusion. Specifically, a rising pitch was hypothesised to produce speeded predicted motion and falling pitch, slowed predicted motion. I investigated the influence of pitch change in vertical and horizontal planes. I also investigated two different aspects of pitch change, since dynamic pitch is a novel addition to TTC paradigms. Experiment 1A explored gradual pitch change and Experiment 1B used sudden pitch change. The hypothesised pitch effects were observed for a gradual, but not a sudden pitch change. However, a gravity effect was observed across both Experiments 1A and 1B, suggesting the presence of sound does not moderate this effect. I also examined the cortical substrates of the audio-visual TTC task components by using transcranial magnetic stimulation (TMS) in Experiment 2. The superior temporal sulcus (STS) was targeted in this experiment, as it has been implicated in audio-visual integration. TMS causes neuronal inhibition, and as such, can be used to determine whether an area is involved in a task. If the STS is responsible for audio-visual integration in a TTC task, then TMS to the STS should disrupt the pitch effects evidenced in Experiment 1A. That is, a change in pitch should have no effect on TTC judgements compared to a constant tone. This result was evident only for rising tones, suggesting the involvement of the STS in the generating speeded predicted motion. The pitch effects observed in Experiment 1A and Experiment 2 implicate pitch in the production of biases in motion imagery for visual motion judgements, particularly for visual stimuli under occlusion.</p>

A linear neural circuit for light avoidance in Drosophila larvae

Understanding how neural circuits underlie behaviour is challenging even in the era of the connectome because it requires a combined approach encompassing anatomical and functional analyses. This is exemplified in studying the circuit underlying the light-avoidance behaviour displayed by the larvae of the fruit fly Drosophila melanogaster. While this behaviour is robust and the nervous system relatively simple, only bits and pieces of the circuit have been delineated1. Indeed, some studies resulted in contradicting conclusions regarding the contributions of various neuronal types to this behaviour2,3. Here we devise trans-Tango MkII, a new version of the transsynaptic circuit tracing and manipulation tool trans-Tango4. We implement trans-Tango MkII in anatomical tracing and combine it with circuit epistasis analysis. We use neuronal inhibition to test necessity of particular neuronal types for light-avoidance. We complement these experiments by selective neuronal activation to examine sufficiency in rescuing light-avoidance deficiencies exhibited by photoreceptor mutants. Together, our studies reveal a four-order, linear circuit for light-avoidance behaviour connecting the light-detecting photoreceptors with a pair of neuroendocrine cells via two types of clock neurons. Our combined approach could be readily expanded to other larval circuits. Further, this strategy provides the framework for studying more complex nervous systems and behaviours.

Cointegration of single-transistor neurons and synapses by nanoscale CMOS fabrication for highly scalable neuromorphic hardware

Cointegration of multistate single-transistor neurons and synapses was demonstrated for highly scalable neuromorphic hardware, using nanoscale complementary metal-oxide semiconductor (CMOS) fabrication. The neurons and synapses were integrated on the same plane with the same process because they have the same structure of a metal-oxide semiconductor field-effect transistor with different functions such as homotype. By virtue of 100% CMOS compatibility, it was also realized to cointegrate the neurons and synapses with additional CMOS circuits. Such cointegration can enhance packing density, reduce chip cost, and simplify fabrication procedures. The multistate single-transistor neuron that can control neuronal inhibition and the firing threshold voltage was achieved for an energy-efficient and reliable neural network. Spatiotemporal neuronal functionalities are demonstrated with fabricated single-transistor neurons and synapses. Image processing for letter pattern recognition and face image recognition is performed using experimental-based neuromorphic simulation.

Association of SLC32A1 Missense Variants With Genetic Epilepsy With Febrile Seizures Plus

ObjectiveTo identify the causative gene in a large unsolved family with genetic epilepsy with febrile seizures plus (GEFS+), we sequenced the genomes of family members, and then determined the contribution of the identified gene to the pathogenicity of epilepsies by examining sequencing data from 2,772 additional patients.MethodsWe performed whole genome sequencing of 3 members of a GEFS+ family. Subsequently, whole exome sequencing (ES) data from 1,165 epilepsy patients from the Epi4K dataset and 1,329 Australian epilepsy patients from the Epi25 dataset was interrogated. Targeted resequencing was performed on 278 patients with FS or GEFS+ phenotypes. Variants were validated and familial segregation examined by Sanger sequencing.ResultsEight previously unreported missense variants were identified in SLC32A1, coding for the vesicular inhibitory amino acid co-transporter VGAT. Two variants co-segregated with the phenotype in 2 large GEFS+ families containing 8 and 10 affected individuals, respectively. Six further variants were identified in smaller families with GEFS+ or idiopathic generalized epilepsy (IGE).ConclusionMissense variants in SLC32A1 cause GEFS+ and IGE. These variants are predicted to alter GABA transport into synaptic vesicles, leading to altered neuronal inhibition. Examination of further epilepsy cohorts will determine the full genotype-phenotype spectrum associated with SLC32A1 variants.

Beta synchrony for expressive language lateralizes to right hemisphere in development

A left perisylvian network is known to support language in healthy adults. Low-beta (13–23 Hz) event-related desynchrony (ERD) has been observed during verb generation, at approximately 700–1200 ms post-stimulus presentation in past studies; the signal is known to reflect increased neuronal firing and metabolic demand during language production. In contrast, concurrent beta event-related synchrony (ERS) is thought to reflect neuronal inhibition but has not been well studied in the context of language. Further, while low-beta ERD for expressive language has been found to gradually shift from bilateral in childhood to left hemispheric by early adulthood, developmental lateralization of ERS has not been established. We used magnetoencephalography to study low beta ERS lateralization in a group of children and adolescents (n = 78), aged 4 to less than 19 years, who performed covert verb generation. We found that the youngest children had bilateral ERD and ERS. By adolescence, low-beta ERD was predominantly left lateralized in perisylvian cortex (i.e., Broca’s and Wernicke’s regions), while beta ERS was predominantly right lateralized. Increasing lateralization was significantly correlated to age for both ERD (Spearman’s r = 0.45, p < 0.01) and ERS (Spearman’s r = − 0.44, p < 0.01). Interestingly, while ERD lateralized in a linear manner, ERS lateralization followed a nonlinear trajectory, suggesting distinct developmental trajectories. Implications to early-age neuroplasticity and neuronal inhibition are discussed.

The Signaling Pathways Involved in the Anticonvulsive Effects of the Adenosine A1 Receptor

Adenosine acts as an endogenous anticonvulsant and seizure terminator in the brain. Many of its anticonvulsive effects are mediated through the activation of the adenosine A1 receptor, a G protein-coupled receptor with a wide array of targets. Activating A1 receptors is an effective approach to suppress seizures. This review gives an overview of the neuronal targets of the adenosine A1 receptor focusing in particular on signaling pathways resulting in neuronal inhibition. These include direct interactions of G protein subunits, the adenyl cyclase pathway and the phospholipase C pathway, which all mediate neuronal hyperpolarization and suppression of synaptic transmission. Additionally, the contribution of the guanyl cyclase and mitogen-activated protein kinase cascades to the seizure-suppressing effects of A1 receptor activation are discussed. This review ends with the cautionary note that chronic activation of the A1 receptor might have detrimental effects, which will need to be avoided when pursuing A1 receptor-based epilepsy therapies.