Impact of lower- vs. upper-hemifield presentation on automatic colour-deviance detection: a visual mismatch...

Area of Science:

• Visual cognitive sciences
• Neuroscience
• Psychology

Background:

• The automatic processing of visual context deviances is crucial for understanding visual cognition.
• The visual mismatch negativity (vMMN), an event-related potential (ERP), is a key measure for investigating this automatic processing.
• vMMN is elicited by infrequent, deviant stimuli within a predictable sequence.

Purpose of the Study:

• To investigate the influence of stimulus presentation in the lower versus upper visual hemifield on the vMMN.
• To explore the underlying neural mechanisms of hemifield-specific vMMN generation.
• To control for spatial attention effects using whole-field stimulus displays.

Main Methods:

• Measurement of vMMN in response to deviant visual stimuli presented in either the lower or upper hemifield.
• Utilized whole-field stimulus displays to minimize spatial attention confounds.
• Employed variable resolution electromagnetic tomography (VARETA) for source localization of brain activity.

Main Results:

• Deviant stimuli in the lower visual hemifield elicited a significantly larger vMMN compared to the upper hemifield (200-280ms latency).
• An earlier hemifield effect (110-150ms) indicated differential processing, with upper-hemifield deviances eliciting a positive potential, unlike lower-hemifield deviances.
• VARETA localized early deviance-related activity to retinotopic visual cortex (BA 17/18) and vMMN sources to occipital regions and higher visual streams.

Conclusions:

• The observed upper/lower hemifield vMMN asymmetry is partly due to hemifield-dependent differences in early visual cortex sensitivity.
• Enhanced automatic processing of lower visual field deviances may also contribute to the observed asymmetry.
• Findings highlight the role of early visual processing stages in generating hemifield-specific responses to contextual deviance.