Variability and Correlations in Primary Visual Cortical Neurons Driven by Fixational Eye Movements

Area of Science:

• Neuroscience
• Systems Neuroscience
• Visual Neuroscience

Background:

• Distinguishing stimulus-driven neural activity from spontaneous fluctuations is crucial in systems neuroscience.
• Standard methods rely on repeated stimulus presentations, assuming identical stimuli across trials.
• Fixational eye movements (FEMs) in awake animals introduce trial-to-trial stimulus variability, challenging this assumption.

Purpose of the Study:

• To develop and validate novel analytical methods for quantifying stimulus-driven and stimulus-independent neural responses in the presence of FEMs.
• To assess the impact of FEMs on measures of neural response reliability and inter-neuron correlations in primary visual cortex (V1).

Main Methods:

• Utilized precise model-based eye tracking to quantify FEMs during neural recordings in awake primate V1.
• Developed new analytical techniques to disentangle stimulus-driven and stimulus-independent neural activity components.
• Applied these methods to neural recordings to analyze response variance and inter-neuron correlations.

Main Results:

• Standard analysis methods ignoring FEMs significantly underestimate stimulus-driven neural response variance in V1.
• FEMs introduce substantial biases in measures of neural response reliability and signal-to-noise ratios.
• Correlations between pairs of V1 neurons are also demonstrably biased by FEMs.

Conclusions:

• FEMs have a dramatic and often overlooked impact on assessing neural activity in awake primates.
• The novel analytical approach effectively controls for FEM-induced confounds in V1 recordings.
• Accurate quantification of signal and noise in visual neurons requires explicit consideration of FEMs.