From an image to a neural response

From a visual stimulus to spikes and a firing rateA tiger image reaches the retina and visual pathway. Use Next step to reveal the recording and then the rate calculation. 1. Present an image 250 ms Retina → LGN → V1 → V2 → V4 → IT IT = inferotemporal cortex; PIT, CIT, AIT are its posterior, central and anterior parts. Simplified route. 2. Record and identify spikes IT electrode · illustrative traceAmplified extracellular voltage Sorted spikes → one neuron (unit) 060220Time after image onset (ms) 3. Estimate firing rate7 spikes in 160 ms160 ms = 0.160 s7 / 0.160 = 43.75 HzHz = spikes per second43.75One unit, one trial

Teaching illustration: the tiger, waveform and spike times do not constitute a recorded Bao trial.

The lateral macaque pathway is DiCarlo, Zoccolan and Rust (2012), Figure 3A. LGN is the lateral geniculate nucleus; V1, V2 and V4 are visual cortical areas; IT is inferotemporal cortex (PIT, CIT and AIT in the source figure). This animation follows one simplified feedforward route, omitting parallel and feedback connections. It does not reproduce measured transmission delays.

An extracellular electrode measures voltage changes near cells. A spike is an action potential. Spike sorting identifies events attributed to an individual neuron. Seven illustrative events in 60–220 milliseconds give 7 / 0.160 = 43.75 spikes per second. Repeated presentations can produce different counts; responses are often averaged across trials.

DiCarlo et al. 2012, Figure 3A · Bao et al. 2020, recording methods