Mirror Neurons in Monkey Premotor Area F5 Show Tuning for Critical Features of Visual Causality Perception

Abstract

Humans derive causality judgments reliably from highly abstract stimuli, such as moving discs that bump into each other [1]. This fascinating visual capability emerges gradually during human development [2], perhaps as consequence of sensorimotor experience [3]. Human functional imaging studies suggest an involvement of the "action observation network" in the processing of such stimuli [4, 5]. In addition, theoretical studies suggest a link between the computational mechanisms of action and causality perception [6, 7], consistent with the fact that both functions require an analysis of sequences of spatiotemporal relationships between interacting stimulus elements. Single-cell correlates of the perception of causality are completely unknown. In order to find such neural correlates, we investigated the responses of "mirror neurons" in macaque premotor area F5 [8, 9]. These neurons respond during the observation as well as during the execution of actions and show interesting invariances, e.g., with respect to the stimulus view [10], occlusions [11], or whether an action is really executed or suppressed [12]. We investigated the spatiotemporal properties of the visual responses of mirror neurons to naturalistic hand action stimuli and to abstract stimuli, which specified the same causal relationships. We found a high degree of generalization between these two stimulus classes. In addition, many features that strongly reduced the similarity of the response patterns coincided with the ones that also destroy the perception of causality in humans. This implies an overlap of neural structures involved in the processing of actions and the visual perception of causality at the single-cell level.

Development of social systems neuroscience using macaques

“…118) Finally, the mirror neurons also fired during the perception of abstract causality stimuli. 120) Together, these findings suggested that mirror neurons can be involved in several aspects of action understanding, including judging the intentionality of the observed action. 121) …”

Visual Neuroscience: Seeing Causality with the Motor System?

“…Having set the stage in Experiment 1, Caggiano et al [6] conducted a second experiment, which revealed the study's core findings. In this experiment, they created abstract versions of the videos by replacing both the hand and the pepper with simple, colored discs (of similar size as the hand and the pepper) that followed the exact same movement trajectories.…”

“…On the basis of spontaneous reports of subjects seeing launching stimuli, Michotte proposed that the detection of causality is an immediate, visual process, rather than a reflective, cognitive one, and that it is innate, rather than acquired through learning [4,5]. In a new study reported in this issue of Current Biology, Caggiano et al [6] discovered neurons that appear to encode visual events with specific causal properties, such as spatiotemporal contingencies. Unexpectedly, these neurons are in the motor cortex, giving a new twist to how we think about the mechanisms giving rise to the perception of causality.…”

“…Unexpectedly, these neurons are in the motor cortex, giving a new twist to how we think about the mechanisms giving rise to the perception of causality. Caggiano et al [6] recorded from neurons in area F5 of the primate brain, which contains large numbers of so-called mirror neurons that respond to both performing a certain action as well as seeing the same action performed. Their monkeys viewed short and highly controlled videos of naturalistic actions.…”

“…While this result is interesting in itself, it suggested an even more intriguing possibility: F5 neurons might encode the causal structure that an action implies. The idea is that the videos used in the experiments (see Supplemental Movie 1 in [6]) generate the perception of causal relations between two stimuli: a disc picks up another disc, or puts it in a new place. In spirit, therefore, these causal events are similar to the launching stimuli introduced by Michotte and used in most subsequent studies of the perception of causality [1][2][3][4][5].…”