Complex object motion represented by context-dependent correlated activity of visual interneurones

Abstract

Accurate and adaptive encoding of complex, dynamic visual information is critical for the survival of many animals. Studies across a range of taxa have investigated behavioral and neuronal responses to objects that represent a threat, such as a looming object approaching along a direct collision course. By investigating neural mechanisms of avoidance behaviors through recording multineuronal activity, it is possible to better understand how complex visual information is represented in circuits that ultimately drive behaviors. We used multichannel electrodes to record from the well‐studied locust nervous system to explore how object motion is reflected in activity of correlated neural activity. We presented locusts (Locusta migratoria) with objects that moved along one of 11 unique trajectories and recorded from descending interneurons within the ventral nerve cord. Spike sorting resulted in 405 discriminated units across 20 locusts and we found that 75% of the units responded to some form of object motion. Dimensionality reduction through principal component (PCA) and dynamic factor (DFA) analyses revealed population vector responses within individuals and common firing trends across the pool of discriminated units, respectively. Population vector composition (PCA) varied with the stimulus and common trends (DFA) showed unique tuning related to changes in the visual size and trajectory of the object through time. These findings demonstrate that this well‐described collision detection system is more complex than previously envisioned and will drive future experiments to explore fundamental principles of how visual information is processed through context‐dependent dynamic ensembles of neurons to initiate and control complex behavior.

Neonicotinoid and sulfoximine pesticides differentially impair insect escape behavior and motion detection

“…Each data point shows the mean habituation index for a single unit across approaches 6 to 10, and asterisks denote a significant effect of treatment within a unit response group. those that touched or expanded past the edge of the ellipse were considered to have a significant stimulus-evoked firing rate change (22). Units that were not responding were removed from subsequent analysis.…”

“…In addition, this neuron habituates to repeated stimulus presentation (19), a phenomenon related to the inhibitory pathways in the optic lobe that are activated in tandem with excitatory pathways (14,20,21). Other descending interneurons can be recorded from the ventral nerve cord with differing response profiles to the DCMD in response to a looming stimulus; however, the population response of these neurons has been examined in only one study (22), and another neuron, the late DCMD, is known to habituate less than the DCMD (23).…”

Three-dimensional shape and velocity changes affect responses of a locust visual interneuron to approaching objects

“…Manipulating object contrast while varying approach velocity or trajectory would address questions regarding neural coding because DCMD responses are consistent for blurred edges (Jones and Gabbiani, 2010) and sensitive to decreases in object coherence , each of which likely exist in the natural visual world. Additionally, simultaneous recordings from multiple neurons in the locust (Dick et al, 2017) will allow for a comparative approach to uncovering neural population coding of complex visual environments, which have been investigated in other systems (Dunn et al, 2016;Liu et al, 2011b).…”