Ming Hsu & W. Jake Jacobs Functional Neuroimaging of Place Learning in a Computer- Generated Space

Introduction u Our experiment employed the use of a Computer-Generated (C-G) Arena in conjunction with fMRI to study the neural structures involved in human place learning. u The C-G Arena was originally designed after the Morris Water Maze (MWZ), an apparatus instrumental in the development of the cognitive mapping theory.

Introduction cont. u We have previously shown that the C-G Arena is a good representation of the human place learning in real space. u We have also shown that people can learn locations within C-G space by observation. u Thus, we took advantage of this close correspondence to mount an fMRI examination of observational place learning.

Introduction cont. u Following the predictions made by cognitive mapping theory, we expect to find activation in the human hippocampus during observational place learning.

Experiment Design u Subjects were shown a recording of a target being found from various locations in the C- G Arena. u Two experimental conditions were used: l 1. Searches in a room that contains a visible target. l 2. Searches in a room that contains an invisible target (i.e., visible only upon contact).

All trials can be roughly divided into thirds. First 1/3 of the trial consists of panning towards the target, second 1/3 shows movement to the target, and the last 1/3 of the trial shows turning while on target. Experiment Design cont. InvisibleKaleidoscopeVisible InvisibleKaleidoscopeVisibleKaleidoscope InvisibleKaleidoscopeVisibleKaleidoscope InvisibleKaleidoscopeVisibleKaleidoscope invisible visiblekaleidoscope

Activation in Perceptual Model Perceptual Model (1) invisible trials - kaleidoscope (2) visible trials - kaleidoscope

Model Subjects MF & RD

Precentral Gyrus Activation MF: vis. v. kal Activation Deactivation Neutral Highest Low Highest MF: inv. v. kal RD: vis v. kal RD: inv v. kal

MF: invisible v. kaleidoscope u Because subject RD did not contain any significant clusters of activation, only activation curves from MF will be shown.

Intraparietal Sulcus Activation Deactivation Neutral Highest Low Highest MF: inv v. kal MF: vis v. kal RD: inv v. kalRD: vis v. kal

MF: invisible v. kaleidoscope Notice again the 2 “bumps” in the activation curves.

RD: invisible v. kaleidoscope RD: inv v. kal Therefore, the latter 1/3 of the trial appears to be crucial for subsequent performance in the CG-Arena

Cerebellum Activation MF: vis_kal RD: inv v. kal MF: inv_kal Activation Deactivation Neutral Highest Low Highest RD: vis v. kal

MF: invisible v. kaleidoscope MF: inv_kal u Again, only MF activation curves will be shown. Cerebellar activity seems to mirror, albeit roughly, the activity in the precentral and parietal areas.

Activation in Learning Model Learning Models (1) first 2 invisible trial - last 2 invisible trials (2) first 2 visible trials - last 2 visible trials

Prefrontal Cortex Activation Deactivation Neutral Highest Low Highest MF: invisible MF: visibleRD: invisible RD: visible

Temporal Lobe: Anterior Activation Deactivation Neutral Highest Low Highest MF: invisible MF: visible RD: invisible RD: visible

Temporal Lobe: Posterior MF: invisible Activation Deactivation Neutral Highest Low Highest MF: visible RD: invisibleRD: visible Activity in temporal lobe appears to be at least an indicator of learning.

MF: MT Activity MF: invisible

Recapitulation uAuActivity in the precentral cortex, and around the intraparietal sulcus during the last 1/3 of the invisible trials is associated with learning. uAuActivity in the prefrontal cortex and temporal cortex in the first 2 invisible trials is also associated with learning.

Conclusions & Hypotheses u “What & Where” System l Ungleider & Mishkin l Dorsal/Parietal = Where. u Therefore, the time when the relationships between the target and cues are established is the crucial period that determines spatial learning. l Ventral/Occipital = What. l Both streams end in inferotemporal cortex, called in monkeys polysensory cortex.

C&H cont. u Parieto-precentral Network: From vision to motion. l Evidence in monkey and imaging literature. l Unanswered questions within the model. u How visual information gets from parietal to precentral cortex, as motor cortex has only access to “blind” areas of parietal lobe.

C&H cont. u Role of temporal lobe l Temporal activity decreases with familiarity in monkey and imaging studies. l In this task, temporal lobe activity appears to be associated primarily with knowledge of spatial relationships among cues and target--difference between invisible and visible trials. l Possibility of cognitive mapping within MT.

C&H cont. u Role of cerebellum l Abundance of cerebellar activity in imaging studies. l Cognition, or fine motor control, or facilitation of cerebral functions? l Possibility of cerebellum as pathway between parietal and precentral areas.

Future directions/questions u How to get hippocampal activation that argues convincingly for (or against) cognitive mapping? u What exactly is the role of cerebellum in all this? u Further elucidation of the existence and function of these networks.

End of Presentation