Naturalizing aesthetics: brain areas for aesthetic appraisal across sensory modalities

Abstract

We present here the most comprehensive analysis to date of neuroaesthetic processing by reporting the results of voxel-based meta-analyses of 93 neuroimaging studies of positive-valence aesthetic appraisal across four sensory modalities. The results demonstrate that the most concordant area of activation across all four modalities is the right anterior insula, an area typically associated with visceral perception, especially of negative valence (disgust, pain, etc.). We argue that aesthetic processing is, at its core, the appraisal of the valence of perceived objects. This appraisal is in no way limited to artworks but is instead applicable to all types of perceived objects. Therefore, one way to naturalize aesthetics is to argue that such a system evolved first for the appraisal of objects of survival advantage, such as food sources, and was later co-opted in humans for the experience of artworks for the satisfaction of social needs.

Fig. 1.

Principal ALE foci for the four sensory-specific meta-analyses. Principal sites of activation are labeled. Talairach z coordinates are shown below each slice. The right side of a slice is the right side of the brain. The threshold is p<0.05, corrected for multiple comparisons using the false discovery rate. Abbreviations (from left to right): IFG: inferior frontal gyrus; IPL, inferior parietal lobule; pgACC, pregenual anterior cingulate cortex; OFC, orbitofrontal cortex; SMA, supplementary motor area; ACC, anterior cingulate cortex.

Fig. 2.

Principal ALE foci for the conjunction analyses. These analyses represent probabilistic maps indicating where binarized FDR-corrected ALE analyses for the four sensory-specific meta-analyses overlap, as registered onto a Talairach-normalized template brain. The right side of a slice is the right side of the brain. A) “2-of-4”, analysis, showing where any two individual meta-analyses overlap. The principal sites of overlap are labeled above each slice. Talairach z coordinates are shown below each slice. The color bar indicates the number of sensory-specific analyses in which overlap occurs. B) “3-of-4” analysis, showing where any three individual meta-analyses overlap. This analysis reveals foci exclusively in the bilateral anterior insula. The boxes to the left and right of the slice indicate the percentage of studies in each meta-analysis showing activation in this region. All four sensory modalities show activation in the right anterior insula. The color bar indicates the number of sensory-specific analyses in which overlap occurs. Abbreviations (from left to right): MCC, midcingulate cortex; NAcc, nucleus accumbens.

Fig. 3.

Logical analysis of ALE foci in the orbitofrontal cortex. ALE foci are displayed for the individual-level ALE analyses for the four sensory modalities in the orbitofrontal cortex and ventral cingulate region, demonstrating the relationship among the modalities. For the four axial slices at right, only the anterior portion of each slice is shown. Talairach z coordinates are shown below the sagittal slice and to the right of each axial slice. The right side of a slice is the right side of the brain. The color coding of the sensory modalities is shown at the bottom left. An overall pattern of adjacency among modalities is observed. However, in the pregenual ACC, gustation overlaps with vision (z = 4) and olfaction (z = −2). In medial OFC, gustation overlaps with audition (z = −14). For simplicity, structures outside of the ventral frontal cortex have been masked in all the slices.

Fig. 4.

The core aesthetic network of the human brain. This is presented as a connectivity model in which aesthetic appraisal is seen as a comparison between exteroceptive information passing through the OFC and interoceptive information passing through the anterior insula. The appraisal of an object‘s valence is assumed to involve recurrent connectivity between these two areas. Also shown in the figure are the rostral/emotional part of the cingulate cortex (BA 32) and the ventral basal ganglia, the latter being one of the “hedonic hotspots” of the brain. This diagram is not meant to represent connectivity in any comprehensive manner. Key limbic areas missing from this diagram include the amygdala, hippocampus, hypothalamus, and basal forebrain. Also missing are general sensory projections to the insula, and visceral afferent projections to the OFC.