Spatial coordinate transforms linking the allocentric hippocampal and egocentric parietal primate brain systems for memory,action in space,and navigation

A theory and model of spatial coordinate transforms in the dorsal visual system through the parietal cortex that enable an interface via posterior cingulate and related retrosplenial cortex to allocentric spatial representations in the primate hippocampus is described. First, a new approach to coordinate transform learning in the brain is proposed, in which the traditional gain modulation is complemented by temporal trace rule competitive network learning. It is shown in a computational model that the new approach works much more precisely than gain modulation alone, by enabling neurons to represent the different combinations of signal and gain modulator more accurately. This understanding may have application to many brain areas where coordinate transforms are learned. Second, a set of coordinate transforms is proposed for the dorsal visual system/parietal areas that enables a representation to be formed in allocentric spatial view coordinates. The input stimulus is merely a stimulus at a given position in retinal space, and the gain modulation signals needed are eye position, head direction, and place, all of which are present in the primate brain. Neurons that encode the bearing to a landmark are involved in the coordinate transforms. Part of the importance here is that the coordinates of the allocentric view produced in this model are the same as those of spatial view cells that respond to allocentric view recorded in the primate hippocampus and parahippocampal cortex. The result is that information from the dorsal visual system can be used to update the spatial input to the hippocampus in the appropriate allocentric coordinate frame, including providing for idiothetic update to allow for self‐motion. It is further shown how hippocampal spatial view cells could be useful for the transform from hippocampal allocentric coordinates to egocentric coordinates useful for actions in space and for navigation.     

Functional anatomy of temporal organisation and domain-specificity of episodic memory retrieval

Episodic memory provides information about the “when” of events as well as “what” and “where” they happened. Using functional imaging, we investigated the domain specificity of retrieval-related processes following encoding of complex, naturalistic events. Subjects watched a 42-min TV episode, and 24 h later, made discriminative choices of scenes from the clip during fMRI. Subjects were presented with two scenes and required to either choose the scene that happened earlier in the film (Temporal), or the scene with a correct spatial arrangement (Spatial), or the scene that had been shown (Object). We identified a retrieval network comprising the precuneus, lateral and dorsal parietal cortex, middle frontal and medial temporal areas. The precuneus and angular gyrus are associated with temporal retrieval, with precuneal activity correlating negatively with temporal distance between two happenings at encoding. A dorsal fronto-parietal network engages during spatial retrieval, while antero-medial temporal regions activate during object-related retrieval. We propose that access to episodic memory traces involves different processes depending on task requirements. These include memory-searching within an organised knowledge structure in the precuneus (Temporal task), online maintenance of spatial information in dorsal fronto-parietal cortices (Spatial task) and combining scene-related spatial and non-spatial information in the hippocampus (Object task). Our findings support the proposal of process-specific dissociations of retrieval.     

"I have often walked down this street before": fMRI studies on the hippocampus and other structures during mental navigation of an old environment

The role of the hippocampus in recent spatial memory has been well documented in patients with damage to this structure, but there is now evidence that the hippocampus may not be needed for the storage and recovery of a spatial layout that was experienced long before injury. Such preservation may rely, instead, on a network of dissociable, extra-hippocampal regions implicated in topographical orientation. Using functional magnetic resonance imaging (fMRI), we investigated this hypothesis in healthy individuals with extensive experience navigating in a large-scale urban environment (downtown Toronto). Participants were scanned as they performed mental navigation tasks that emphasized different types of spatial representations. Tasks included proximity judgments, distance judgments, landmark sequencing, and blocked-route problem-solving. The following regions were engaged to varying degrees depending on the processing demands of each task: retrosplenial cortex, believed to be involved in assigning directional significance to locales within a relatively allocentric framework; medial and posterior parietal cortex, concerned with processing space within egocentric coordinates during imagined movement; and regions of prefrontal cortex, present in tasks heavily dependent on working memory. In a second, event-related experiment, a distinct area of inferotemporal cortex was revealed during identification of familiar landmarks relative to unknown buildings in addition to activation of many of those regions identified in the navigation tasks. This result suggests that familiar landmarks are strongly integrated with the spatial context in which they were experienced. Importantly, right medial temporal lobe activity was observed, its magnitude equivalent across all tasks, though the core of the activated region was in the parahippocampal gyrus, barely touching the hippocampus proper.     

Egocentric memory impaired and allocentric memory intact as assessed by virtual reality in subjects with unilateral parietal cortex lesions

Present evidence suggests that medial temporal cortices subserve allocentric representation and memory, whereas egocentric representation and memory mainly depends on inferior and superior parietal cortices. Virtual reality environments have a major advantage for the assessment of spatial navigation and memory formation, as computer-simulated first-person environments can simulate navigation in a large-scale space. However, virtual reality studies on allocentric memory in subjects with cortical lesions are rare, and studies on egocentric memory are lacking. Twenty-four subjects with unilateral parietal cortex lesions due to infarction or intracerebral haemorrhage (14 left-sided, 10 right-sided) were compared with 36 healthy matched control subjects on two virtual reality tasks affording to learn a virtual park (allocentric memory) and a virtual maze (egocentric memory). Subjects further received a comprehensive clinical and neuropsychological investigation, and MRI lesion assessment using T₁, T₂ and FLAIR sequences as well as 3D MRI volumetry at the time of the assessment. Results indicate that left- and right-sided lesioned subjects did not differ on task performance. Compared with control subjects, subjects with parietal cortex lesions were strongly impaired learning the virtual maze. On the other hand, performance of subjects with parietal cortex lesions on the virtual park was entirely normal. Volumes of the right-sided precuneus of lesioned subjects were significantly related to performance on the virtual maze, indicating better performance of subjects with larger volumes. It is concluded that parietal cortices support egocentric navigation and imagination during spatial learning in large-scale environments.     

Egocentric and allocentric memory as assessed by virtual reality in individuals with amnestic mild cognitive impairment

Present evidence suggests that medial temporal cortices subserve allocentric representation and memory, whereas egocentric representation and memory also depends on parietal association cortices and the striatum. Virtual reality environments have a major advantage for the assessment of spatial navigation and memory formation, as computer-simulated first-person environments can simulate navigation in a large-scale space. Twenty-nine patients with amnestic MCI (aMCI) were compared with 29 healthy matched controls on two virtual reality tasks affording to learn a virtual park (allocentric memory) and a virtual maze (egocentric memory). Participants further received a neuropsychological investigation and MRI volumetry at the time of the assessment. Results indicate that aMCI patients had significantly reduced size of the hippocampus bilaterally and the right-sided precuneus and inferior parietal cortex. aMCI patients were severely impaired learning the virtual park and the virtual maze. Smaller volumes of the right-sided precuneus were related to worse performance on the virtual maze. Participants with striatal lacunar lesions committed more errors than participants without such lesions on the virtual maze but not on the virtual park. aMCI patients later converting to dementia (n = 15) had significantly smaller hippocampal size when compared with non-converters (n = 14). However, both groups did not differ on virtual reality task performance. Our study clearly demonstrates the feasibility of virtual reality technology to study spatial memory deficits of persons with aMCI. Future studies should try to design spatial virtual reality tasks being specific enough to predict conversion from MCI to dementia and conversion from normal to MCI.     

Memory for familiar environments learned in the remote past: fMRI studies of healthy people and an amnesic person with extensive bilateral hippocampal lesions

Preserved remote spatial memory in amnesic people with bilateral hippocampal damage, including the well-studied case K.C., challenges spatial theories, which assume that the hippocampus is needed to support all allocentric spatial representations, old or new. It remains possible, however, that residual hippocampal tissue is functional and contributes to successful performance. Here, we examine brain activity with fMRI during the retrieval of spatial information in K.C. and in healthy controls using landmark and route stimuli from a premorbidly familiar neighborhood that K.C. can navigate normally. In all participants, activity was found in the parahippocampal cortex, but not in the hippocampus itself, during all navigational tasks on which K.C. performs well, even though part of his hippocampus remains viable. The opposite pattern was observed on a house recognition task, which is inconsequential to navigation, and on which K.C. performed poorly. On that task, K.C. recruited the right hippocampus presumably because even "familiar" houses were treated as novel by him, whereas controls recruited occipitotemporal cortex, including parahippocampal cortex. The distinction between recent and remote memory, therefore, may apply as much to spatial theories of hippocampal function as it does to theories emphasizing the role of the hippocampus in other types of explicit memory.     

Involvement of the hippocampus and associative parietal cortex in the use of proximal and distal landmarks for navigation

Rats with dorsal hippocampus or associative parietal cortex (APC) lesions and sham-operated controls were trained on variants of the Morris water maze navigation task. In the 'proximal landmark condition', the rats had to localize the hidden platform solely on the basis of three salient object landmarks placed directly in the swimming pool. In the 'distal landmark condition', rats could rely only on distal landmarks (room cues) to locate the platform. In the 'beacon condition', the platform location was signaled by a salient cue directly attached to it. Rats with hippocampal lesions were impaired in the distal and to a less extent in the proximal landmark condition whereas rats with parietal lesions were impaired only in the proximal landmark condition. None of the lesioned groups was impaired in the beacon condition. These results suggest that the processing of information related to proximal, distal landmarks or associated beacon are mediated by different neural systems. The hippocampus would contribute to both proximal and distal landmark processing whereas the APC would be involved in the processing of proximal landmarks only. Navigation relying on a cued-platform would not require participation of the hippocampus nor the APC. Assuming that the processing of proximal landmarks heavily depends on the integration of visuospatial and idiothetic information, these results are consistent with the hypothesis that the APC plays a role in the combination of multiple sensory information and contributes to the formation of an allocentric spatial representation.     

Neural substrates for allocentric‐to‐egocentric conversion of remembered reach targets in humans

Targets for goal‐directed action can be encoded in allocentric coordinates (relative to another visual landmark), but it is not known how these are converted into egocentric commands for action. Here, we investigated this using a slow event‐related fMRI paradigm, based on our previous behavioural finding that the allocentric‐to‐egocentric (Allo–Ego) conversion for reach is performed at the first possible opportunity. Participants were asked to remember (and eventually reach towards) the location of a briefly presented target relative to another visual landmark. After a first memory delay, participants were forewarned by a verbal instruction if the landmark would reappear at the same location (potentially allowing them to plan a reach following the auditory cue before the second delay), or at a different location where they had to wait for the final landmark to be presented before response, and then reach towards the remembered target location. As predicted, participants showed landmark‐centred directional selectivity in occipital–temporal cortex during the first memory delay, and only developed egocentric directional selectivity in occipital–parietal cortex during the second delay for the ‘Same cue’ task, and during response for the ‘Different cue’ task. We then compared cortical activation between these two tasks at the times when the Allo–Ego conversion occurred, and found common activation in right precuneus, right presupplementary area and bilateral dorsal premotor cortex. These results confirm that the brain converts allocentric codes to egocentric plans at the first possible opportunity, and identify the four most likely candidate sites specific to the Allo–Ego transformation for reaches.     

The Precuneus and Visuospatial Attention in Near and far Space: A Transcranial Magnetic Stimulation Study

BackgroundThere is a large body of evidence for the involvement of the parietal cortex in orientation and navigation in space. This has been supplemented by investigation of the contribution of a number of subregions using transcranial magnetic stimulation.ObjectiveThe role of the precuneus area, located in the medial plane of posterior parietal cortex (PPC), in visuospatial functions is not well understood. We investigated the contribution of this area using the landmark task.MethodsParticipants were asked to make forced-choice judgments of which side of prebisected line was longer for near and far viewing conditions (70 and 180 cm, respectively). Online 10 Hz, repetitive transcranial magnetic stimulation (rTMS) was delivered for 500 ms over the right precuneus, rPPC and vertex (control), in separate blocks of trials. The rPPC stimulation was used as a positive control, having previously resulted in “neglect like” spatial bias effects in a number of studies.ResultsA no-TMS condition showed a leftward spatial bias (pseudoneglect) for near space judgments but not for far space and was used as the baseline. Precuneus stimulation resulted in rightward spatial bias from the midpoint in near space similar to the rPPC neglect-like effect. No significant effects were seen with vertex stimulation.ConclusionThis study shows that precuneus, like other parietal areas, is involved in visuospatial functions. Further work is required to clarify how the contribution of this area differs from other parietal regions.     

Cerebellar‐hippocampal processing in passive perception of visuospatial change: An ego‐ and allocentric axis?

In addition to its role in visuospatial navigation and the generation of spatial representations, in recent years, the hippocampus has been proposed to support perceptual processes. This is especially the case where high‐resolution details, in the form of fine‐grained relationships between features such as angles between components of a visual scene, are involved. An unresolved question is how, in the visual domain, perspective‐changes are differentiated from allocentric changes to these perceived feature relationships, both of which may be argued to involve the hippocampus. We conducted functional magnetic resonance imaging of the brain response (corroborated through separate event‐related potential source‐localization) in a passive visuospatial oddball‐paradigm to examine to what extent the hippocampus and other brain regions process changes in perspective, or configuration of abstract, three‐dimensional structures. We observed activation of the left superior parietal cortex during perspective shifts, and right anterior hippocampus in configuration‐changes. Strikingly, we also found the cerebellum to differentiate between the two, in a way that appeared tightly coupled to hippocampal processing. These results point toward a relationship between the cerebellum and the hippocampus that occurs during perception of changes in visuospatial information that has previously only been reported with regard to visuospatial navigation.     

Do parietal cortical lesions impair spatial attention or allocentric spatial perception?

It remains unclear whether monkeys with large parietal cortical lesions fail "landmark" tasks because they cannot judge the relative distances between landmark and response locations, or because they fail to attend to, or even to notice, the landmark. Monkeys with small posterior parietal (SPP), large posterior parietal (LPP), superior temporal sulcus (STS), or frontal eye field (FEF) lesions were tested on a landmark task in which the physical salience of the landmark and its location varied. Only the LPP monkeys were impaired, seemingly because they overtly failed to shift attention during each trial, responding to whichever food well they looked at first. A task based on one used with neurological patients was therefore introduced in which the monkeys had to discriminate between two white square plaques each containing a spot, where the spot on the positive stimulus was centrally placed. Solving this task requires an allocentric judgement about the relative location of each spot to the edges of the plaque. Even on the most difficult discrimination, monkeys with large parietal lobe lesions were unimpaired. The deficits previously reported on landmark tasks probably reflect a failure of spatial attention or attention to objects rather than an inability to judge allocentric spatial relationships.     

Transcranial Direct Current Stimulation Modulates Activation and Effective Connectivity During Spatial Navigation

BackgroundAllocentric navigation declines with age and neurologic disease whereas egocentric navigation does not; differences that likely arise from maladaptive changes in brain regions mediating spatial (parietal cortex; hippocampus) but not procedural processing (caudate nucleus). Transcranial direct current stimulation (tDCS) holds promise for treating such decline given its ability to modulate neuronal excitability, but its effects have yet to be examined on spatial navigation.Objectives/hypothesesUsing healthy young adults as a model, Study 1 intended to validate a novel spatial navigation paradigm using functional magnetic resonance imaging (fMRI). Using these data to determine targets for tDCS, Study 2 aimed to determine if 1) stimulation modulates activation in a polarity-specific manner; 2) stimulation results in global and/or task-specific activation changes; 3) activation changes are accompanied by changes in effective connectivity.MethodsAll participants underwent fMRI while learning allocentric and egocentric environments. Twelve participants completed Study 1. In Study 2, 16 participants were randomized to 20 min of tDCS (2 mA) using a montage with the anode over PZ and cathode over AF4 (P+F−) or the reverse montage (P−F+).ResultsStudy 1 revealed that distinct networks preferentially mediate allocentric and egocentric navigation. Study 2 revealed polarity-dependent changes in activation and connectivity. The P+F− montage increased these measures in spatial regions, especially during allocentric navigation, and the caudate nucleus. Conversely, the P−F+ montage increased activation and connectivity in lateral prefrontal cortices and posterior hippocampus.ConclusionsThese findings support the neuromodulatory effects of tDCS in non-motor areas and demonstrate proof-of-principle for ameliorating age- and disease-related decline in navigational abilities.     

The hippocampus is involved in mental navigation for a recently learned, but not a highly familiar environment: a longitudinal fMRI study

Functional magnetic resonance imaging (MRI) was used to investigate the hypothesis that memory for a large-scale environment is initially dependent on the hippocampus but is later supported by extra-hippocampal structures (e.g., precuneus, posterior parahippocampal cortex, and lingual gyrus) once the environment is well-learned. Participants were scanned during mental navigation tasks initially when they were newly arrived to the city of Toronto, and later after having lived and navigated within the city for 1 yr. In the first session, activation was observed in the right hippocampus, left precuneus, and postcentral gyrus. The second session revealed activation in the caudate and lateral temporal cortex, but not in the right hippocampus; additional activation was instead observed in the posterior parahippocampal cortex, lingual gyrus, and precuneus. These findings suggest that the right hippocampus is required for the acquisition of new spatial information but is not needed to represent this information when the environment is highly familiar.     

Cholinergic modulation of spatial learning,memory and navigation

Spatial learning, including encoding and retrieval of spatial memories as well as holding spatial information in working memory generally serving navigation under a broad range of circumstances, relies on a network of structures. While central to this network are medial temporal lobe structures with a widely appreciated crucial function of the hippocampus, neocortical areas such as the posterior parietal cortex and the retrosplenial cortex also play essential roles. Since the hippocampus receives its main subcortical input from the medial septum of the basal forebrain (BF) cholinergic system, it is not surprising that the potential role of the septo‐hippocampal pathway in spatial navigation has been investigated in many studies. Much less is known of the involvement in spatial cognition of the parallel projection system linking the posterior BF with neocortical areas. Here we review the current state of the art of the division of labour within this complex ‘navigation system’, with special focus on how subcortical cholinergic inputs may regulate various aspects of spatial learning, memory and navigation.     

Immediate memory for “when,where and what”: Short‐delay retrieval using dynamic naturalistic material

We investigated the neural correlates supporting three kinds of memory judgments after very short delays using naturalistic material. In two functional magnetic resonance imaging (fMRI) experiments, subjects watched short movie clips, and after a short retention (1.5–2.5 s), made mnemonic judgments about specific aspects of the clips. In Experiment 1, subjects were presented with two scenes and required to either choose the scene that happened earlier in the clip (“scene‐chronology”), or with a correct spatial arrangement (“scene‐layout”), or that had been shown (“scene‐recognition”). To segregate activity specific to seen versus unseen stimuli, in Experiment 2 only one probe image was presented (either target or foil). Across the two experiments, we replicated three patterns underlying the three specific forms of memory judgment. The precuneus was activated during temporal‐order retrieval, the superior parietal cortex was activated bilaterally for spatial‐related configuration judgments, whereas the medial frontal cortex during scene recognition. Conjunction analyses with a previous study that used analogous retrieval tasks, but a much longer delay (>1 day), demonstrated that this dissociation pattern is independent of retention delay. We conclude that analogous brain regions mediate task‐specific retrieval across vastly different delays, consistent with the proposal of scale‐invariance in episodic memory retrieval. Hum Brain Mapp 36:2495–2513, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.     

Increased Hippocampal Excitability and Altered Learning Dynamics Mediate Cognitive Mapping Deficits in Human Aging

Learning the spatial layout of a novel environment is associated with dynamic activity changes in the hippocampus and in medial parietal areas. With advancing age, the ability to learn spatial environments deteriorates substantially but the underlying neural mechanisms are not well understood. Here, we report findings from a behavioral and a fMRI experiment where healthy human older and younger adults of either sex performed a spatial learning task in a photorealistic virtual environment (VE). We modeled individual learning states using a Bayesian state-space model and found that activity in retrosplenial cortex (RSC)/parieto-occipital sulcus (POS) and anterior hippocampus did not change systematically as a function learning in older compared with younger adults across repeated episodes in the environment. Moreover, effective connectivity analyses revealed that the age-related learning deficits were linked to an increase in hippocampal excitability. Together, these results provide novel insights into how human aging affects computations in the brain''s navigation system, highlighting the critical role of the hippocampus.SIGNIFICANCE STATEMENT Key structures of the brain''s navigation circuit are particularly vulnerable to the deleterious consequences of aging, and declines in spatial navigation are among the earliest indicators for a progression from healthy aging to neurodegenerative diseases. Our study is among the first to provide a mechanistic account about how physiological changes in the aging brain affect the formation of spatial knowledge. We show that neural activity in the aging hippocampus and medial parietal areas is decoupled from individual learning states across repeated episodes in a novel spatial environment. Importantly, we find that increased excitability of the anterior hippocampus might constitute a potential neural mechanism for cognitive mapping deficits in old age.     

Spatial Learning Drives Rapid Goal Representation in Hippocampal Ripples without Place Field Accumulation or Goal-Oriented Theta Sequences

The hippocampus is critical for rapid acquisition of many forms of memory, although the circuit-level mechanisms through which the hippocampus rapidly consolidates novel information are unknown. Here, the activity of large ensembles of hippocampal neurons in adult male Long-Evans rats was monitored across a period of rapid spatial learning to assess how the network changes during the initial phases of memory formation and retrieval. In contrast to several reports, the hippocampal network did not display enhanced representation of the goal location via accumulation of place fields or elevated firing rates at the goal. Rather, population activity rates increased globally as a function of experience. These alterations in activity were mirrored in the power of the theta oscillation and in the quality of theta sequences, without preferential encoding of paths to the learned goal location. In contrast, during brief “offline” pauses in movement, representation of a novel goal location emerged rapidly in ripples, preceding other changes in network activity. These data demonstrate that the hippocampal network can facilitate active navigation without enhanced goal representation during periods of active movement, and further indicate that goal representation in hippocampal ripples before movement onset supports subsequent navigation, possibly through activation of downstream cortical networks.SIGNIFICANCE STATEMENT Understanding the mechanisms through which the networks of the brain rapidly assimilate information and use previously learned knowledge are fundamental areas of focus in neuroscience. In particular, the hippocampal circuit is a critical region for rapid formation and use of spatial memory. In this study, several circuit-level features of hippocampal function were quantified while rats performed a spatial navigation task requiring rapid memory formation and use. During periods of active navigation, a general increase in overall network activity is observed during memory acquisition, which plateaus during memory retrieval periods, without specific enhanced representation of the goal location. During pauses in navigation, rapid representation of the distant goal well emerges before either behavioral improvement or changes in online activity.     

Distinct neural systems underlie learning visuomotor and spatial representations of motor skills

Motor skill learning depends upon acquiring knowledge about multiple features of sequential behaviors, including their visuomotor and spatial properties. To investigate the neural systems that distinguish these representations, we carried out functional magnetic resonance imaging (fMRI) as healthy adults learned to type sequences on a novel keyboard. On the initial training day, learning-related changes in brain activation were found in distributed cortical regions, only a subset of which correlated with improvements in movement time (MT), suggesting their preeminence in controlling movements online. Subjects received extended training on the sequences during the ensuing week, after which they returned to the scanner for another imaging session. Relative to performance at the end of the first training day, continued plasticity was most striking in the inferior parietal cortex and new areas of plasticity were uncovered in the caudate and cerebellum. Plasticity in these regions correlated with reaction time (RT), suggesting their role in planning sequences before movement onset. Two transfer conditions probed for "what" subjects learned. The probe for visuomotor learning produced increased activation in visual analysis (left inferior visual cortex) and advance planning (left caudate) systems. The probe for spatial learning produced increased activation in visuomotor-transformation (left dorsal visual pathway) and retrieval (left precuneus) systems. Increased activity in all of these regions correlated with increased RT, but not MT, indicating that both transfer conditions interfered with the neural representation of plans for the sequences, but not processes that controlled their implementation. These findings demonstrated that neuroanatomically dissociable systems support the acquisition of visuomotor and spatial representations of actions.     

Representation of Contralateral Visual Space in the Human Hippocampus

The initial encoding of visual information primarily from the contralateral visual field is a fundamental organizing principle of the primate visual system. Recently, the presence of such retinotopic sensitivity has been shown to extend well beyond early visual cortex to regions not historically considered retinotopically sensitive. In particular, human scene-selective regions in parahippocampal and medial parietal cortex exhibit prominent biases for the contralateral visual field. Here, we used fMRI to test the hypothesis that the human hippocampus, which is thought to be anatomically connected with these scene-selective regions, would also exhibit a biased representation of contralateral visual space. First, population receptive field (pRF) mapping with scene stimuli revealed strong biases for the contralateral visual field in bilateral hippocampus. Second, the distribution of retinotopic sensitivity suggested a more prominent representation in anterior medial portions of the hippocampus. Finally, the contralateral bias was confirmed in independent data taken from the Human Connectome Project (HCP) initiative. The presence of contralateral biases in the hippocampus, a structure considered by many as the apex of the visual hierarchy, highlights the truly pervasive influence of retinotopy. Moreover, this finding has important implications for understanding how visual information relates to the allocentric global spatial representations known to be encoded therein.SIGNIFICANCE STATEMENT Retinotopic encoding of visual information is an organizing principle of visual cortex. Recent work demonstrates this sensitivity in structures far beyond early visual cortex, including those anatomically connected to the hippocampus. Here, using population receptive field (pRF) modeling in two independent sets of data we demonstrate a consistent bias for the contralateral visual field in bilateral hippocampus. Such a bias highlights the truly pervasive influence of retinotopy, with important implications for understanding how the presence of retinotopy relates to more allocentric spatial representations.