Using Live and Video Stimuli to Localize Face and Object Processing Regions of the Canine Brain

Abstract

Previous research to localize face areas in dogs’ brains has generally relied on static images or videos. However, most dogs do not naturally engage with two-dimensional images, raising the question of whether dogs perceive such images as representations of real faces and objects. To measure the equivalency of live and two-dimensional stimuli in the dog’s brain, during functional magnetic resonance imaging (fMRI) we presented dogs and humans with live-action stimuli (actors and objects) as well as videos of the same actors and objects. The dogs (n = 7) and humans (n = 5) were presented with 20 s blocks of faces and objects in random order. In dogs, we found significant areas of increased activation in the putative dog face area, and in humans, we found significant areas of increased activation in the fusiform face area to both live and video stimuli. In both dogs and humans, we found areas of significant activation in the posterior superior temporal sulcus (ectosylvian fissure in dogs) and the lateral occipital complex (entolateral gyrus in dogs) to both live and video stimuli. Of these regions of interest, only the area along the ectosylvian fissure in dogs showed significantly more activation to live faces than to video faces, whereas, in humans, both the fusiform face area and posterior superior temporal sulcus responded significantly more to live conditions than video conditions. However, using the video conditions alone, we were able to localize all regions of interest in both dogs and humans. Therefore, videos can be used to localize these regions of interest, though live conditions may be more salient.

Functionally analogous body- and animacy-responsive areas in the dog (Canis familiaris) and human occipito-temporal lobe

“…We further identified three occipito-temporal regions with a preference for faces and bodies compared to inanimate objects. By adding bodies as stimuli, and thus controlling for animacy, our findings crucially expand those from earlier investigations on face perception in dogs 34–, 39 , and suggest that previously identified face-sensitive areas respond more generally to animate entities. In humans, we replicated previous work localizing multiple distinct face- and body-sensitive regions (e.g., 8 for review).…”

“…Research so far suggests an involvement of dogs' temporal lobe in face perception, but inconclusive results have triggered a debate on whether the occipitotemporal specialization for face perception in dogs matches that of humans [34][35][36][37][38] . In brief, prior work did not find greater activation for faces compared to scrambled images 34,35 , but compared to scenes 35 or objects 35,37,39 , or didn't have any non-facial controls 36 , questioning if face-sensitivity rather reflects differences in low-level visual properties. Further, almost all prior studies lacked animate stimuli other than faces [34][35][36][37]39 and the only study 38 with another animate stimulus category (i.e., the back of the head) had no inanimate control condition.…”

“…In brief, prior work did not find greater activation for faces compared to scrambled images 34,35 , but compared to scenes 35 or objects 35,37,39 , or didn't have any non-facial controls 36 , questioning if face-sensitivity rather reflects differences in low-level visual properties. Further, almost all prior studies lacked animate stimuli other than faces [34][35][36][37]39 and the only study 38 with another animate stimulus category (i.e., the back of the head) had no inanimate control condition. Thus, studies so far could not control for animacy as an alternate explanation of the supposed face-sensitive responses.…”

“…Results regarding species preferences were also mixed, ranging from no conspecific-preference 35 to separate regions for dog and human face perception 36 and a recent report of a conspecific-preferring visual region 38 . Therefore, previous studies carry several limitations that prevent a better understanding of how dogs perceive others compared to humans: they cannot disentangle face-sensitive from general animate vs. inanimate perception, are inconclusive regarding perception of con- and hetero-specific individuals, and provide limited insights into potentially convergent neural underpinnings of face perception, with only two comparative studies so far 38, 39 .…”

Action observation reveals a network with divergent temporal and parietal lobe engagement in dogs compared to humans

“…Second, we hypothesized that the dog action observation network, as in humans, includes occipito-temporal brain areas associated with faceand body perception (i.e., agent areas), as well as areas involved in processing of dynamic aspects of social cues and action features [6][7][8] . First evidence suggests that the dog agent areas are housed in the occipito-temporal ectomarginal, the mid and caudal suprasylvian gyrus, but results have been mixed [42][43][44][45][46][47][48][49] . Brain areas associated with the processing of dynamic aspects have yet to be investigated.…”