Expected and unexpected uncertainty in the human hippocampus
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1
University if Queensland, Queensland Brain Institute, Australia
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2
University College London, Wellcome Trust Centre for Neuroimaging, United Kingdom
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3
University College London, Institute of Cognitive Neuroscience, United Kingdom
Background: We are sure to face uncertainty in a constantly changing world. The ability to detect changes is fundamental for adaptive behaviour and the failure to tolerate uncertainty has been associated with anxiety disorders and schizophrenia. Different forms of uncertainty, expected and unexpected, have been proposed to evoke qualitatively different brain signals and segregation of specific neuromodulators. Neuroimaging studies have shown that the hippocampus is involved in mismatch computations and that hippocampal theta oscillations are modulated in novel environments.
Methods: We use magnetocencephalography (MEG) to investigate the oscillatory activity in the hippocampus under different forms of uncertainty: expected and unexpected. While performing an incidental task, participants were presented with predictable (ABCD), surprising (ABDC), or random (CADB) sequences of objects. Surprising sequences of objects elicit a mismatch, or unexpected uncertainty, whereas random sequences evoke expected uncertainty due to a predicted change. We used linear constrained minimum variance (LCMV) Beamforming to reconstruct images of theta, alpha, beta, and gamma oscillatory source activity from MEG data recorded in a sample of healthy individuals (N=16). We then looked for specific effects of expected and unexpected uncertainty in the hippocampus.
Results: We found that anterior hippocampal theta was significantly higher for the unexpected than the predictable condition. Posterior hippocampal theta, on the other hand, was higher for the unexpected when compared to the ‘expected uncertainty’ condition. Crucially, these effects were found specifically in theta and not in other frequency bands.
Conclusions: Our findings build upon ideas of functional segregation down the long axis of the hippocampus, by linking generic novelty or change detection to theta modulation in the anterior hippocampus, and prediction violation or mismatch computations to theta modulation in the posterior hippocampus.
Keywords:
uncertainty,
expectation,
mismatch,
Magnetoencephalography (MEG),
Hippocampus
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Oral
Topic:
Executive Processes
Citation:
Garrido
M,
Barnes
G,
Kumaran
D,
Maguire
E and
Dolan
R
(2013). Expected and unexpected uncertainty in the human hippocampus.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00159
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Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Dr. Marta Garrido, University if Queensland, Queensland Brain Institute, St Lucia, Australia, marta.garrido@unimelb.edu.au