Biology subjects

Supple, J. A.

Publications and source records attributed to Supple, J. A..

6 recordsLinked to original sources

bioRxiv2026

Breadboard Neuroscience: Exploring Neuronal Dynamics and Computation with Simple Electronic Circuits

Simple electronic circuits provide a tangible means of exploring the electrical principles underlying neuronal signalling and computation. Here is presented a sequence of experiments using inexpensive, readily available components assembled on solderless breadboards to investigate passive membrane properties and analogue neural computation. A resistor-capacitor membrane model demonstrates how membrane resistance, capacitance, and excitatory conductance determine response amplitude and charging and discharging time constants. Multiple inputs illustrate sublinear summation and shunting inhibition. Connecting membrane compartments through axial resistances reproduces spatial attenuation and temporal delay. We then construct an elementary motion detector to demonstrate how simple electrical operations can produce direction-selective responses to visual motion. Together, this approach offers an accessible and flexible platform for exploring neuronal biophysics, allowing students to relate mathematical descriptions to observable electrical behaviour whilst developing practical electronics skills and engaging creatively in the design of their own experiments.

neuroscience↗

bioRxiv2026

The Effective Visual Acuity of Butterflies in Flight

The spatial visual acuity of an eye is determined by both the spatial sampling density of the retina and the angular sensitivity of individual photoreceptors. In insect compound eyes, these are respectively characterised by the interommatidial angle, {Delta}{varphi}, and photoreceptor acceptance angle, {Delta}{rho}. During movement, however, finite photoreceptor integration times cause retinal image motion to broaden the effective acceptance angle, potentially degrading spatial resolution beyond its anatomical limit. This problem is especially acute in flying insects, which experience large rotational velocities during locomotion and must actively stabilise gaze to limit retinal image motion. Butterflies present a particularly demanding case because their flight is characterised by large, wingbeat-coupled thoracic oscillations. Here, we quantify how gaze stabilisation limits motion blur in freely flying Monarch butterflies Danaus plexippus by combining free-flight kinematic reconstruction of the head and thorax with separate intracellular measurements of photoreceptor acceptance angles and integration times from quiescent butterflies. We found that, without head compensation, thoracic oscillations would broaden the effective photoreceptor acceptance angle from its quiescent value of 2.17{degrees} to 9.38{degrees} during take-off. Compensatory head movements substantially reduced this motion-induced broadening, limiting the effective acceptance angle to 5.28{degrees}. Nevertheless, this 2.4-fold broadening of effective photoreceptor acceptance angle represents a substantial degradation of spatial acuity in flight, highlighting motion blur as an important constraint on the visual ecology of flying butterflies.

neuroscience↗

bioRxiv2026

Wing mechanosensory modulation of optic flow-sensitive descending neurons in butterflies

Visual motion processing in flying insects is strongly modulated by behavioural state, yet the mechanisms by which mechanosensory feedback contributes to this modulation remain poorly understood. Here we show that wing mechanosensation alone is sufficient to modulate a subset of optic flow-sensitive descending neurons (WFDNs) in butterflies. Airflow stimulation of the wings, mimicking flight conditions, increased baseline firing rates and reduced response latencies in WFDNs, without altering response gain or temporal frequency tuning. These effects indicate that mechanosensory modulation acts through mechanisms distinct from those governing other state-dependent changes in visual processing. Consistent with this interpretation, previous work has shown that baseline firing and response latency can be rapidly modulated, whereas gain changes arise through slower neuromodulatory pathways. Mechanosensory modulation was cell-type specific: the horizontally tuned WFDNL neuron was consistently affected across individuals, whereas other WFDN types were largely insensitive, likely reflecting the unilateral airflow stimuli used here. Interestingly, WFDNL modulation arose exclusively from mechanosensory input from the proximal area of the wing, not from distal wing deformation. This suggests that descending visual pathways require only coarse gain or excitability modulation rather than detailed information about wing shape or strain, leaving fast reflexive control of distal wing deformation to local ganglionic circuits. Together, our results demonstrate that wing mechanosensation selectively modulates visual descending pathways by altering excitability and timing rather than visual feature encoding, supporting the existence of multiple, parallel mechanisms for state-dependent visual modulation during flight.

neuroscience↗

bioRxiv2025

Spectral Matched Filtering in the Butterfly Visuomotor System

Color provides an important dimension for object detection and classification. In most animals, color- and motion-vision are largely separated throughout early stages of visual processing. However, accumulating evidence indicates crosstalk between chromatic and achromatic pathways. Here we investigate the spectral sensitivity of the butterfly motion-vision pathway at the level of pre-motor descending neurons (DNs), which connect the brain to thoracic motor centres. Butterflies engage in fast agile flight within often-colorful visual ecologies, which may heighten evolutionary pressure to integrate color- and motion-vision. Indeed, we observed a separation of spectral sensitivities that matches the functional properties of butterfly DNs, such that wide-field optic flow-sensitive DNs involved in stabilisation reflexes have effectively broadband spectral responses, whilst target-selective DNs involved in target-tracking are comparatively narrowband and match conspecific wing coloration. Our findings demonstrate an integration of color- and motion-vision within a pre-motor neuronal bottleneck that controls behavior.

neuroscience↗

bioRxiv2025

Adaptive feedforward speed control in Drosophila

Insects demonstrate remarkable agility in flight despite constant changes in flight dynamics throughout their lives. However, it is unclear whether such resilience is conferred via purely feedback control or whether adaptive feedforward control mechanisms are present. This study examines whether adaptive feedforward control mechanisms are present in Drosophila melanogaster flight, by comparing the free-flight trajectories with and without wing damage and antennae ablation. Flies with partial wing excisions exhibited increased flight speeds in the dark compared to intact-wing controls. Upon exposure to visual contrast in light, the clipped-wing flies reduced their speed comparable to that of the control group flies. Notably, the lower speed persisted upon returning to the dark, indicating an enduring change to the flight controller. To discern between feedforward adaptation and a change in mechanosensory feedback gains, we replicated the experiment after ablating the antennal arista, the primary mechanosensors for sensing airspeed. Although flies with ablated antennae flew with greater variance in speed, they displayed a parallel trend in mean speed adaptation: increased speed in the dark, compensation in the light, and sustained lower speed in subsequent dark conditions. This consistent pattern strongly supports the involvement of adaptive feedforward control rather than the adjustment of mechanosensory feedback gains. Our investigation unveils an adaptive strategy in D. Melanogaster flight, illustrating its ability to set flight speed through adaptive feedforward control mechanisms.

bioengineering↗

bioRxiv2022

Generating spatiotemporal patterns of linearly polarised light at high frame rates for insect vision research

Polarisation vision is commonplace among invertebrates; however, most experiments focus on determining behavioural and/or neurophysiological responses to static polarised light sources rather than moving patterns of polarised light. To this end, we designed a polarisation stimulation device based on superimposing polarised and non-polarised images from two projectors, which can display moving patterns at frame rates exceeding invertebrate flicker fusion frequencies. A linear polariser fitted to one projector enables moving patterns of polarised light to be displayed, whilst the other projector contributes arbitrary intensities of non-polarised light to yield moving patterns with a defined polarisation and intensity contrast. To test the device, we measured receptive fields of polarisation sensitive Argynnis paphia butterfly photoreceptors for both non-polarised and polarised light. We then measured local motion sensitivities of the optic flow-sensitive lobula plate tangential cell H1 in Calliphora vicina blowflies under both polarised and non-polarised light, finding no polarisation sensitivity in this neuron.

neuroscience↗