Abstract
Actions transform objects in predictable ways, allowing us to generate visual expectations about the consequences of our actions. In a recent study (Hindy et al., 2016, Nature Neurosci), we found that such expectations in visual cortex were signaled by the hippocampus. However, that study examined action-based prediction (i) for novel associations and (ii) among arbitrarily paired stimuli. The hippocampus may have been involved only because of these factors, as they are critical aspects of its role in episodic memory. An alternative account is that the hippocampus is always involved in action-based prediction, regardless of the nature of the underlying memories, given its unique computational abilities, such as for pattern completion. Here we evaluate these accounts in two high-resolution fMRI experiments, considering both novel transformations, as in previous work, and known transformations involving long-term semantic knowledge. One experiment utilized novel transformations between distinct-looking stimuli (e.g., "point" or "wave" transformed a newspaper into a cookie or carrot), whereas known transformations were between visually similar stimuli ("bite" or "break" transformed a whole carrot into one bitten or broken). A second experiment utilized novel transformations between visually similar stimuli (e.g., "smile" or "frown" transformed a t-shirt into one rolled-up or folded), whereas known transformations were between distinct-looking stimuli (e.g., "fry" or "mash" transformed a potato into French fries or mashed potatoes). For both novel and known transformations, responses in early visual cortex were attenuated when an outcome could be predicted from an action, and this predictive attenuation was related to background connectivity with the hippocampus. However, over the long axis of the hippocampus, there were anterior-posterior differences across conditions. Our findings are thus partly consistent with both of the accounts above: hippocampal involvement in action-based prediction seems ubiquitous, but the nature of this involvement can depend on the age and similarity of memories.
Meeting abstract presented at VSS 2018