Mental Scene and Memory Construction and the Hippocampus A neurocomputational theory of scene and memory construction during memory recall, prospective thinking, and autobiographical memory is described. The theory describes the nature of the representation of scenes using spatial view cells in a continuous attractor network in the medial parahippocampal cortex, and how the location in the scene being represented can be shifted by self-motion eye position update even when the scene is not visible. The theory builds on the evidence for humans for a ventromedial visual cortical scene pathway via the prostriate cortex and ventromedial visual cortical regions to the medial parahippocampal scene (or place) area where scenes are represented. The approach builds on a theory about how visual features in scenes are used along this pathway to build a continuous attractor network representation of scenes in the medial parahippocampal cortex that represents the relative spatial locations of features or landmarks in the scene. The theory shows how episodic memory can be built in an attractor network in hippocampal CA3 that learns associations between the location in a scene (“where”), the object or person at that location in the scene (“what”), and the reward/affective value conveyed to the hippocampus from the orbitofrontal cortex in part via the ventromedial prefrontal cortex and posterior cingulate cortex. The theory of scene construction then shows how backprojections from hippocampal CA1 via the entorhinal cortex to the medial parahippocampal cortex can recall or construct the scene representation in the medial parahippocampal cortex, the parahippocampal scene (or place) area; and how whole memories including visual imagery of objects, rewards, and their locations in scenes can be constructed by iterative neocortical-hippocampal-neocortical processing.
Retrieval-related Eye Movements Are Predictive of Memory Precision Eye movements are predictive of successful episodic memory encoding and retrieval, but it is unclear whether they reflect the precision of retrieved memory content. Here, we examined relationships between eye fixations, memory precision, and fMRI BOLD activity. At study, participants were presented with object images, each placed at a random location on a circle. At test, both studied and new images were presented. Participants were instructed to recall and signal the studied location of each image, guessing if necessary. They then indicated if the image had been studied. Simultaneous fMRI and eye-tracking data were acquired during the test phase. For correctly recognized images, trial-wise angular distances between the studied and reported locations were fitted to a two-component mixture model. On the basis of model-derived parameters, correctly recognized images were categorized as those associated with successful location retrieval (location hits) or guesses. Location hits were further divided into high- and low-precision trials. At retrieval, fixation location predicted both successful retrieval and the precision of the retrieved location memory. In addition, across-trial fixation patterns were more similar for location hits than for guesses and for high- than for low-precision trials. The association between retrieval success and fixation precision was evident across almost the entire recall phase, whereas memory precision effects emerged around 1–1.5 sec after image onset. Fixation precision and pattern similarity each predicted trial-wise memory precision independently of hippocampal BOLD activity, which also predicted memory precision. Taken together, the findings indicate that eye movements during retrieval track the fidelity of retrieved mnemonic content.
Modality-specific reactive and predictive responses in the human superior colliculus Inspired by recent theoretical work emphasizing predictive neural processing, we tested whether a midbrain structure for multimodal sensory integration—the superior colliculus—would show predictive responses to both visual and somatosensory stimulation. A multi-stage experimental design allowed us to test predictive activity in the human superior colliculus while 7-Tesla functional magnetic resonance imaging (fMRI) allowed us to map its sensory response across superior colliculus layers (N = 80). As expected from non-human animal work, visual and somatosensory stimulation elicited distinct depth-dependent responses. We also observed a predictive response: these same modality-specific and depth-dependent effects occurred during task periods preceding direct stimulation, when sensorimotor input was identical between visual and somatosensory conditions. Further analyses rule out cross-trial carryover and show corresponding effects in the thalamic sensory nuclei. Here our results confirm that, in humans, the superior colliculus is sensitive to both visual and somatosensory input, and they demonstrate that it carries predictive signals for upcoming sensory events.
Clarifying the scope and boundaries of the motor simulation theory: A constructive perspective for motor imagery research Motor imagery has attracted renewed interest in recent years, along with renewed debate about the Motor Simulation Theory, which posits activation of motor-related neural systems to internally simulate action without execution. While recent work has clarified some empirical limits of imagery, particularly in feedback-based learning, other critiques misinterpret the theory’s core assumptions. This paper distinguishes between empirically grounded challenges that refine the Motor Simulation Theory, such as those involving executive processes and partial motor activation, and conceptual misunderstandings that mischaracterize the theory. Claims that the theory predicts exact timing equivalence or complete neural overlap with action execution, or supports sensorimotor adaptation overlook the functional equivalence principle at its foundation. We also argue that alternative, behaviorally focused theories often neglect robust neurophysiological evidence underpinning the Motor Simulation Theory. We advocate for an integrated perspective that maintains its predictive value while accommodating valid critiques, aiming to clarify its boundaries and relevance for imagery research.
Investigating the Effects of Acute Stress on Neural Mechanisms of Self-controlled Decision-making Successfully exerting self-control is an important prerequisite for adaptive decision-making in daily life. The experience of acute stress might impair the ability to select actions in line with personally valued long-term goals in situations where a conflict between short-term and long-term action consequences arises. In this fMRI study, we examined the effects of experimentally induced acute stress on neural and behavioral substrates of self-controlled decision-making in a large sample (n = 175). We showed that acute stress was associated with increased modulation of activation in the ventromedial PFC by anticipated action short-term consequences, suggesting that acute stress might alter the degree to which short-term consequences are incorporated into the neural valuation process, but not with decreased modulation by long-term consequences. In addition, acute stress reduced functional connectivity between ventromedial and dorsolateral PFCs during self-control conflict possibly indicating weakened recruitment of cognitive control. However, despite group differences on the neural level, acute stress did not affect the impact of anticipated short-term or long-term action consequences on behavioral decisions or participants’ self-control performance. Several factors might have contributed to the results reported here, for instance, potential compensatory mechanisms employed by stressed participants. Future work is needed to address these systematically.rk efficiency, and associations with standardized language ability were small and mixed in direction.
Equidistance between primary sensory-motor landmarks shapes functional specialisation in the human brain The human cortex is organized around primary sensory–motor landmarks, but the way these distances shape large-scale functional organization remains unclear. Using geodesic measures in males and females, we show that global minimum distance to sensory–motor landmarks aligns with the principal gradient of intrinsic connectivity, reflecting the shift from unimodal to heteromodal cortex, while equidistance between landmarks captures complementary organizational patterns. Heteromodal networks, including default mode, control, and limbic systems, occupy cortical regions that are both distant from primary systems and relatively balanced between them. Subsystems within these networks exhibit distinctive spatial embeddings: core default mode regions sit equidistant between visual and somatomotor cortex, frontotemporal default mode regions favour auditory cortex but remain relatively balanced, and medial temporal regions are biased toward visual cortex. Control network subsystems also vary: the control–DMN subsystem occupies the most distant and equidistant positions, core control is closer to motor regions, and medial control is closer to visual cortex, reflecting their different functional specializations. At the parcel level, greater equidistance predicts stronger task-evoked activation, particularly in heteromodal border zones. These findings highlight two complementary spatial principles — proximity and balance — that structure the cortex, shaping both the location and functional profile of heteromodal networks.
Hippocampal and prefrontal contributions to memory-guided navigation depend on task epoch The hippocampus and medial prefrontal cortex (mPFC) are required for delayed working-memory tasks, but when in the task their engagement becomes necessary remains an open question. We trained mice on a delayed cue-guided T-maze navigation task and used transient optogenetic silencing to test the contribution of the mPFC and hippocampus during distinct task epochs. Surprisingly, silencing during the delay period did not impair performance. In contrast, perturbation during the early phase of the central arm traversal produced robust deficits. Mice made more perseverative choices, slowed their speed and ran farther down the track before turning towards the selected arm. Control experiments showed that these effects could not be explained by the manipulation targeting elapsed time and were rather specific to task phase. These results indicate that hippocampal and prefrontal contributions to memory-guided behavior are not uniform across the trial, but instead depend on task epoch. More broadly, they suggest that the functional engagement of these circuits is gated by behavioral state or context.
Dopamine release-associated striatal blood oxygenation and whole-brain dynamics during associative learning Dopaminergic signaling in the nucleus accumbens (NAc) is central to reward-based learning, but its relationship to brain-wide hemodynamics remains unclear. Using concurrent fMRI and dopamine photometry in awake, behaving mice, we reveal that associative learning induces a gradual temporal shift in NAc blood oxygenation responses that mirrors dopamine release dynamics. This shift emerges with cue-reward learning and extends across a distributed network encompassing the lateral septal complex, as well as prefrontal, insular, and hypothalamic regions. Further, dopamine transients tightly correspond with local blood oxygenation level dependent (BOLD) signals, and variations in reward value modulate delayed BOLD responses in both the NAc and additional subcortical structures. Regressing out the measured dopaminergic signal abolishes this reward-related modulation, suggesting that BOLD signals track dopaminergic reward prediction. These findings reveal a close relationship between dopamine signaling and widespread changes in brain activity during learning.