Effect of lamotrigine on cognition in children with epilepsy

Abstract

<h3>Abstract</h3> Colour is a defining feature of many objects, playing a crucial role in our ability to rapidly recognise things in the world around us and make categorical distinctions. For example, colour is a vital cue when distinguishing lemons from limes or blackberries from raspberries. That means our representation of many objects includes key colour-related information. The question addressed here is whether the neural representation activated by <i>knowing</i> that something is red is the same as that activated when we <i>actually see</i> something red, particularly in regard to timing. We addressed this question using neural timeseries (magnetoencephalography, MEG) data to contrast real colour perception and implied object colour activation. We applied multivariate pattern analysis (MVPA) to focus, in particular, on the temporal dynamics of these processes. Male and female human participants (N=18) viewed isoluminant red and green shapes and grey-scale, luminance-matched pictures of fruits and vegetables that are red (e.g., tomato) or green (e.g., kiwifruit) in nature. We show that the brain activation pattern evoked by real colour perception is similar to implied colour activation, but that this pattern is instantiated at a later time. Similarly, participants were faster at categorising the colour of an abstract shape than they were at categorising the typical colour of grey-scale objects. Together, these results demonstrate that a common colour representation can be triggered by activating object representations from memory and perceiving colours. We show here that the key difference between these processes lies in the time it takes to access the common colour representation. <h3>Significance Statement</h3> Colour is a defining feature of objects and is vital to rapidly recognise and categorise things in our environment. In the current study, we recorded neural data to contrast the <i>timecourse</i> of colour representations when evoked by colour perception versus object-colour activation. We found that the neural representation for coloured shapes is similar to that of grey-scale images of objects that are associated with a colour (e.g., red for a tomato). However, the common colour representation is activated later when accessed via object-colour knowledge in comparison to colour perception, consistent with the idea that they are evoked when the object representation is accessed. These results highlight the critical role of perceptual features such as colour in conceptual object representations.