Abstract
Lateralization of brain functions has been suggested to provide individuals with advantages, such as an increase of neural efficiency. The right hemisphere is likely to be specialized for processing attention for details and the left hemisphere for categorization of stimuli. Thus attentional processes actually may underlie lateralization. In the present study, we hypothesized that the attentional state of horses could be reflected in the lateralization of brain responses. We used i) a recently developed attention test to measure horses’ visual attentional responses towards a standardized stimulus and ii) a recently developed portable EEG telemetric tool to measure brain responses. A particular emphasis was given to the types of waves (EEG power profile) and their side of production when horses were either attentive towards a visual stimulus or quiet standing. The results confirmed that a higher attentional state is associated with a higher proportion of gamma waves. There was moreover an interaction between the attentional state, the hemisphere and the EEG profile: attention towards the visual stimulus was associated with a significant increase of gamma wave proportion in the right hemisphere while “inattention” was associated with more alpha and beta waves in the left hemisphere. These first results are highly promising and contribute to the large debate on functional lateralization.
Highlights
Lateralization of brain functions appears as a key property of most vertebrates[1] as well as of invertebrates[2]
The left hemisphere is supposed to be specialized in categorizing information and responds more to features that are invariant and repeated, while the right hemisphere responds more to novel events and the expression of intense emotional states such as aggression, escape behaviour and fear[3,6]
Functional brain asymmetry may be affected by age
Summary
Lateralization of brain functions appears as a key property of most vertebrates[1] as well as of invertebrates[2]. Some basic patterns of lateralization seem to exist in terms of attention, emotion[1], or nature of the cognitive task performed[3,4,5]. Strongly lateralized individuals have been shown to have enhanced efficiency when performing dual tasks[13] and lateralization may enhance cognition in general[14]. Rogers[15] showed that vigilance while pecking at food was better in chicks with lateralization of visual processing than in chicks that were not so lateralized, in relation to a specialization of the right hemisphere for attention to details, and of the left hemisphere for categorization of stimuli. Authors proposed that given that attention is related to wakefulness, attention processes underlie lateralization
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