The approximate number system (ANS), which supports the rapid estimation of quantity, emerges early in human development and is widespread across species. Neural evidence from both human and non-human primates suggests the parietal cortex as a primary locus of numerical estimation, but it is unclear whether the numerical competencies observed across non-primate species are subserved by similar neural mechanisms. Moreover, because studies with non-human animals typically involve extensive training, little is known about the spontaneous numerical capacities of non-human animals. To address these questions, we examined the neural underpinnings of number perception using awake canine functional magnetic resonance imaging. Dogs passively viewed dot arrays that varied in ratio and, critically, received no task-relevant training or exposure prior to testing. We found evidence of ratio-dependent activation, which is a key feature of the ANS, in canine parietotemporal cortex in the majority of dogs tested. This finding is suggestive of a neural mechanism for quantity perception that has been conserved across mammalian evolution.
Given humans' habitual use of screens, they rarely consider potential differences when viewing two dimensional (2D) stimuli and real-world versions of dimensional stimuli. Dogs also have access to many forms of screens and touch pads, with owners even subscribing to dog-directed content. Humans understand that 2D stimuli are representations of real-world objects, but do dogs? In canine cognition studies, 2D stimuli are almost always used to study what is normally 3D, like faces, and may assume that both 2D and 3D stimuli are represented in the brain the same way. Here, we used awake fMRI of 15 dogs to examine the neural mechanisms underlying dogs' perception of two-and three-dimensional objects after the dogs were trained on either a two-or three-dimensional version of the objects. Activation within reward processing regions and parietal cortex of the dog brain to 2D and 3D versions of objects was determined by their training experience, as dogs trained on one dimensionality showed greater activation to the dimension on which they were trained. These results show that dogs do not automatically generalize between two-and three-dimensional stimuli and caution against implicit assumptions when using pictures or videos with dogs.
The perception and representation of objects in the world are foundational to all animals. The relative importance of objects' physical properties versus how the objects are interacted with continues to be debated. Neural evidence in humans and nonhuman primates suggests animate-inanimate and face-body dimensions of objects are represented in the temporal cortex. However, because primates have opposable thumbs and interact with objects in similar ways, the question remains as to whether this similarity represents the evolution of a common cognitive process or whether it reflects a similarity of physical interaction. Here, we used functional magnetic resonance imaging (fMRI) in dogs to test whether the type of interaction affects object processing in an animal that interacts primarily with its mouth. In Study 1, we identified object-processing regions of cortex by having dogs passively view movies of faces and objects. In Study 2, dogs were trained to interact with two new objects with either the mouth or the paw. Then, we measured responsivity in the object regions to the presentation of these objects. Mouth-objects elicited significantly greater activity in object regions than paw-objects. Mouth-objects were also associated with activity in somatosensory cortex, suggesting dogs were anticipating mouthing interactions. These findings suggest that object perception in dogs is affected by how dogs expect to interact with familiar objects.
Given humans’ habitual use of screens, they rarely consider potential differences when viewing two dimensional (2D) stimuli and real-world versions of dimensional stimuli. Dogs also have access to many forms of screens and touch pads, with owners even subscribing to dog-directed content. Humans understand that 2D stimuli are representations of real-world objects, but do dogs? In canine cognition studies, 2D stimuli are almost always used to study what is normally 3D, like faces, and may assume that both 2D and 3D stimuli are represented in the brain the same way. Here, we used awake fMRI of 15 dogs to examine the neural mechanisms underlying dogs’ perception of two- and three-dimensional objects after the dogs were trained on either a two- or three-dimensional version of the objects. Activation within reward processing regions and parietal cortex of the dog brain to 2D and 3D versions of objects was determined by their training experience, as dogs trained on one dimensionality showed greater activation to the dimension on which they were trained. These results show that dogs do not automatically generalize between two- and three-dimensional stimuli and caution against implicit assumptions when using pictures or videos with dogs.
47The approximate number system, which supports the rapid estimation of quantity, emerges early 48 in human development and is widespread across species. Neural evidence from both human and 49 non-human primates suggests the parietal cortex as a primary locus of numerical estimation, but 50 it is unclear whether the numerical competencies observed across non-primate species are 51 subserved by similar neural mechanisms. Moreover, because studies with non-human animals 52 typically involve extensive training, little is known about the spontaneous numerical capacities 53 of non-human animals. To address these questions, we examined the neural underpinnings of 54 number perception using awake canine functional magnetic resonance imaging. Dogs passively 55 viewed dot arrays that varied in ratio and, critically, received no task-relevant training or 56 exposure prior to testing. We found evidence of ratio-dependent activation, which is a key 57 feature of the approximate number system, in canine parietotemporal cortex in the majority of 58 dogs tested. This finding is suggestive of a neural mechanism for quantity perception that has 59 been conserved across mammalian evolution. 60 61 Keywords: approximate number system; canine cognition; quantity discrimination; fMRI; 62 parietal cortex 63 93 of cortex for representing non-symbolic numerical quantity, then activation in this region should 94 increase as the ratio between alternating dot arrays increases, despite constant cumulative surface 95 area and variable element size [17]. That is, a number-sensitive region of cortex will exhibit 96 greater activation when the numerical values of the stimuli presented are more dissimilar (e.g., 2 97 vs. 10 dots) than when numerical value is constant (e.g., 6 vs. 6 dots), consistent with Weber's 98 law [18]. 99 100 Methods 101 Participants 102 103 Eleven awake, unrestrained dogs (see Table 1 for demographic information), were 104 scanned in a Siemens 3T Trio MRI scanner. Prior to testing, all dogs completed a training 105 program to be desensitized to the scanner environment through behavior shaping and positive 106 reinforcement [19]. All dogs had previously participated in fMRI studies while viewing stimuli 107 on a projection screen but had no prior training on numerical discrimination. 108 109 Table 1. Dogs' demographic information Stimuli were 75 dot arrays comprised of light gray dots on a black background (800 x 130 800 px). For each numerosity used (2, 4, 6, 8, and 10), stimuli varied in cumulative area (i.e., the 131 total gray on each image). For each numerosity, cumulative area was either 10, 20, or 30% of the 132 total stimulus. For each numerosity, 15 unique stimuli were used (5 stimuli per cumulative area 133 value). In each stimulus, individual dot size varied up to 30%. Dot location varied randomly. 134Critically, these controls minimize the influence of non-numerical properties, in order to ensure 135 that the results can be attributed to changes in numerical value [20, 21]. In accordance with 136 current esti...
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