Our Faces in the Dog's Brain: Functional Imaging Reveals Temporal Cortex Activation during Perception of Human Faces

<div><p>Dogs have a rich social relationship with humans. One fundamental aspect of it is how dogs pay close attention to human faces in order to guide their behavior, for example, by recognizing their owner and his/her emotional state using visual cues. It is well known that humans have specific brain regions for the processing of other human faces, yet it is unclear how dogs’ brains process human faces. For this reason, our study focuses on describing the brain correlates of perception of human faces in dogs using functional magnetic resonance imaging (fMRI). We trained seven domestic dogs to remain awake, still and unrestrained inside an MRI scanner. We used a visual stimulation paradigm with block design to compare activity elicited by human faces against everyday objects. Brain activity related to the perception of faces changed significantly in several brain regions, but mainly in the bilateral temporal cortex. The opposite contrast (i.e., everyday objects against human faces) showed no significant brain activity change. The temporal cortex is part of the ventral visual pathway, and our results are consistent with reports in other species like primates and sheep, that suggest a high degree of evolutionary conservation of this pathway for face processing. This study introduces the temporal cortex as candidate to process human faces, a pillar of social cognition in dogs.</p></div

Visual stimulation paradigm.

<p>We used a block paradigm constituted by two types of blocks: Human faces and Objects. Each block was presented for 7 s, and it was composed of 4 different images (i.e., each image was visible for 1.75 s). At the beginning of each run and after each block, a fixation screen was presented for 12.25 s. The total duration of each run was 190 s, and each dog experienced 5 runs in total. Photographs of faces are reprinted from the AR face database [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149431#pone.0149431.ref021" target="_blank">21</a>] under a CC BY license, with permission from the author.</p

Location of the most sensitive region for faces in each participant in the temporal cortex.

<p><b>A-C:</b> Left lateral, anterior and right lateral views showing spheres of 5 mm radius in each hemisphere, colored differently for each dog. <b>D:</b> BOLD signal change in both hemispheres in response to faces and objects within the sphere of each participant. Lines represent the data of each dog, colors according to spheres in A-C. Vertical lines represent the standard error (*** < 0.001).</p

Complete fMRI dataset of one awake dog during visual stimulation.

<div><br></div><div>Data corresponding to article:</div><div>"Our Faces in the Dog's Brain: Functional imaging reveals temporal cortex activation during perception of human faces".</div><div>PLoS ONE 2016.</div><div><table><tbody><tr><td>10.1371/journal.pone.0149431<br><br></td></tr></tbody></table></div><div><br></div><div>Includes: anatomic image, fMRI images (5 runs) and vector files. </div><div><br></div><div>F1-F5 indicate run number.</div><div>V1-V3 indicate corresponding stimulation paradigm (txt files)</div><div><br></div><div>All image files are in Nifti format. </div><div>For any question or more data [email protected]</div

Training procedure for awake dog fMRI.

<p>During a period of approximately four months, dogs learned to stay still and attend to a visual stimulation paradigm within the MRI scanner. First, dogs learned to rest their chin and avoid movement (<b>A</b>), followed by habituation to the scanning environment, including scanner sounds and the use of protective headphones, in a mock MRI scanner (<b>B</b>). Next, dogs were further trained within the real MRI scanner (<b>C</b>) and habituated to the imaging coils (<b>D</b>). Upon completion of training, all dogs were able to lie still and awake for periods of up to 15 minutes.</p

Bilateral temporal cortex in the contrast Human faces > Objects (n = 7).

<p>The cerebral activity focused in the temporal cortex is shown overlaid on the Datta atlas [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149431#pone.0149431.ref024" target="_blank">24</a>]. <b>A.</b> Left hemisphere in a sagittal slice. <b>B.</b> Bilateral temporal cortex in a coronal slice. <b>C.</b> Right hemisphere in a sagittal slice. Dashed lines in B show the location of the sagittal slices shown in A and C. <b>D.</b> BOLD signal change in a sphere of 5 mm radius sphere centered at the voxel with maximum <i>z</i> value for the both hemispheres (blue spheres show in A, B and C). Oblique lines represent the data of each participant and vertical lines represent standard error. * < 0.05; ** < 0.01.</p

Human faces > Objects (n = 7).

<p>The two largest resulting clusters are shown overlaid on the Datta atlas [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149431#pone.0149431.ref024" target="_blank">24</a>]. <b>A.</b> Sagittal slice of the temporal cluster, which shows activity within the left temporal and frontal cortices. <b>B.</b> Coronal slice shows the left temporal cluster, which extends to the thalamus. <b>C.</b> BOLD signal change in a 5 mm of radius sphere around the voxel with maximum <i>z</i> value for the left temporal cluster (blue sphere in A and B). <b>D.</b> Sagittal slice of the frontal cluster, which is located in the right frontal temporal and cortices. <b>E.</b> Coronal slice of the frontal cluster. <b>F.</b> BOLD signal change in a 5 mm of radius sphere around the voxel with maximum <i>z</i> value for the right frontal cluster (blue sphere in D and E). <b>G-I.</b> Volume renderings of the same results, seen in left lateral, basal and right lateral views, respectively. S = Superior, I = Inferior, L = Left, R = Right, P = Posterior and, A = Anterior. 1 = Temporal Cortex, 2 = Thalamus, 3 = Lateral Frontal Cortex, 4 = Temporal Cortex, 5 = Medial Frontal Cortex. The oblique lines in C and F represent data of each participant, while vertical lines denote the standard error (*** < 0.001, **<0.01).</p