Daniel Sjölie

Remembering our origin: Gender differences in spatial memory are reflected in gender differences in hippocampal lateralization

Gender differences in spatial memory favoring men are frequently reported, and the involvement of the hippocampus in these functions is well-established. However, little is known of whether this behavioral gender difference is mirrored in a gender difference in hippocampal function. Here we assessed hippocampal activity, using functional MRI, while 24 men and women moved through three-dimensional virtual mazes (navigation phase) of varying length, and at the end-point estimated the direction of the starting-point (pointing phase). Men were indeed more accurate than women at estimating direction, and this was especially true in longer mazes. Both genders activated the posterior hippocampus throughout the whole task. During the navigation phase, men showed a larger activation in the right hippocampus than women, while in the pointing phase, women showed a larger activation in the left hippocampus than men. Right-lateralized activation during the navigation phase was associated with greater task performance, and may reflect a spatial strategy that is beneficial in this task. Left-sided activation during the pointing phase might reflect a less efficient post hoc verbal recapitulation of the route. This study is the first to identify neural correlates of the commonly observed male advantage in recalling ones original position, and points to hippocampal lateralization as a possible explanation for this behavioral gender difference.

Neurocognitive Systems Related to Real-World Prospective Memory

Background Prospective memory (PM) denotes the ability to remember to perform actions in the future. It has been argued that standard laboratory paradigms fail to capture core aspects of PM. Methodology/Principal Findings We combined functional MRI, virtual reality, eye-tracking and verbal reports to explore the dynamic allocation of neurocognitive processes during a naturalistic PM task where individuals performed errands in a realistic model of their residential town. Based on eye movement data and verbal reports, we modeled PM as an iterative loop of five sustained and transient phases: intention maintenance before target detection (TD), TD, intention maintenance after TD, action, and switching, the latter representing the activation of a new intention in mind. The fMRI analyses revealed continuous engagement of a top-down fronto-parietal network throughout the entire task, likely subserving goal maintenance in mind. In addition, a shift was observed from a perceptual (occipital) system while searching for places to go, to a mnemonic (temporo-parietal, fronto-hippocampal) system for remembering what actions to perform after TD. Updating of the top-down fronto-parietal network occurred at both TD and switching, the latter likely also being characterized by frontopolar activity. Conclusion/Significance Taken together, these findings show how brain systems complementary interact during real-world PM, and support a more complete model of PM that can be applied to naturalistic PM tasks and that we named PROspective MEmory DYnamic (PROMEDY) model because of its dynamics on both multi-phase iteration and the interactions of distinct neurocognitive networks.

Presence and general principles of brain function

Recent developments in general theories of cognition and brain function make it possible to consider the concept of presence from a new perspective, based in general principles of brain function. The importance of interaction with reality for the development and function of the brain and human cognition is increasingly emphasized. The brain is explained as implementing a generative model of the current environment. Whether this environment is real or virtual does not matter. Mental simulations are created for whatever one interacts with, when possible. This view provides a basis for relating human experiences in virtual environments to several theories that explain cognition and brain function on many levels, from ultimate evolutionary motivations to plausible neural implementations. The purpose of this paper is not to provide yet another definition of presence but to suggest explanations of phenomena commonly related to presence, with a basis in general principles of brain function. Such principles are employed to explain how, and why, interaction with our environment, and internalization of objects and tools therein, play an essential role in human cognition. This provides a rich basis for further analysis of how central aspects of presence, such as breaks in presence or the perceptual illusion of non-mediation, may work on a fundamental level. More general descriptions of such phenomena have advantages such as being easier to relate to new contexts and technologies, and opening up for additional inspiration and confirmation from other disciplines such as cognitive neuroscience. In addition to an account of general principles for brain function and a discussion about the concept of presence in light of these, this paper also relates this discussion to a number of previous accounts of presence, and to practical implications and applications for interaction design.

Effects of interactivity and 3D-motion on mental rotation brain activity in an immersive virtual environment

The combination of virtual reality (VR) and brain measurements is a promising development of HCI, but the maturation of this paradigm requires more knowledge about how brain activity is influenced by parameters of VR applications. To this end we investigate the influence of two prominent VR parameters, 3d-motion and interactivity, while brain activity is measured for a mental rotation task, using functional MRI (fMRI). A mental rotation network of brain areas is identified, matching previous results. The addition of interactivity increases the activation in core areas of this network, with more profound effects in frontal and preparatory motor areas. The increases from 3d-motion are restricted to primarily visual areas. We relate these effects to emerging theories of cognition and potential applications for brain-computer interfaces (BCIs). Our results demonstrate one way to provoke increased activity in task-relevant areas, making it easier to detect and use for adaptation and development of HCI.