Temperature-induced shifts and temperature compensation in the tuning of motion-sensitive neurons of bumblebees.

Bumblebees are poikilothermic insects, i.e., their body temperature generally follows the ambient temperature. However, within certain boundaries, bumblebees are able to increase their body temperature above the ambient temperature through shivering thermogenesis. Biophysical processes, including neuronal activity, depend on temperature. In the past, the influence of temperature on sensory systems and neuronal coding was investigated in different insect species. Most studies described a temperature dependency of neuronal responses, yet some behavioral processes require robust encoding of information. Here we investigated the influence of temperature on the tuning of wide-field motion-sensitive neurons in the central brain of bumblebees. Using multiunit recordings, we examined neuronal tuning properties to translational motion by presenting moving gratings at two head temperature conditions. Although the tuning of most neurons showed a temperature dependency, some neurons stayed unaffected within the tested temperature range. In a third group of neurons the tuning was not affected by temperature for one movement direction of the stimulus, whereas the response to the opposite direction was temperature dependent. These different response types might serve different behavioral functions. Neurons that are involved in the control of self-motion might require temperature-dependent response properties, because bumblebees fly faster at higher temperatures and therefore experience faster optic flow. Other behaviors that rely on optic flow (e.g., measuring distance traveled) require a robust, temperature-independent encoding of optic flow information. Hence, neurons that respond largely independently of temperature are required for this task. Our findings suggest a function-dependent level of temperature compensation in different populations of motion-sensitive neurons.NEW & NOTEWORTHY Bumblebees need to cope with varying temperatures of their body and head, which depend both on ambient temperature and on self-generated heat. To investigate the impact of changing head temperature on response properties of motion-sensitive neurons in the bumblebee central brain we used multiunit recordings to measure responses at different temperatures. We show that the bumblebee central brain comprises both temperature-dependent and temperature-compensated motion-sensitive neurons, which might account for different behavioral functions.