Extracellular Recordings
Neurons communicate via small electric pulses, called action potentials or spikes. In general, a neuron generates a spike (or many of them) when it receives sufficiently strong input at its synapses. Neuronal activity results in changes in the composition of ions in extracellular space and thereby in local variations of the electric field, which can be measured. Such extracellular recordings provide access to the activity of single cells and allow the investigation of communication between individual neurons and groups of neurons with very high spatio-temporal resolution. This is key to understand the neuronal mechanisms subserving cognitive functions, as e.g. attention-dependent improvement of neuronal response selectivity and signal-to noise ratio, coordination of activity in neuronal ensembles, and communication within and across brain areas (e.g. Grothe et al., 2012; Drebitz et al., 2018; Galashan et al., 2013; Schledde et al., 2017).
![Onset response of visual neurons to a stimulus which is presented on a screen.](/fileadmin/_processed_/8/d/csm_OnsetV1CSD_12ad767b0e.jpg)
![Rezeptives Feld eines V1 Neurons The map shows the visual area of a neuron to which it responses. The center of gaze is slighlty above the responsive region](/fileadmin/_processed_/7/e/csm_V1RF_01_4be11fdf54.jpg)
![The spiking activity of neurons located in the visual middle temporal area. These neurons are very sensitive to motions and changes in speed. The shown trace depicts their activity (firing rate) in response to a moving grating, which accelerated in speed.](/fileadmin/_processed_/3/0/csm_PSTH_cce04062c6.jpg)