Elevated Insulin Levels Engage the Salience Network during Multisensory Perception

Neuroendocrinology, vol. 114, pp. 90–106

Abstract

INTRODUCTION: Brain insulin reactivity has been reported in connection with systematic energy metabolism, enhancement in cognition, olfactory sensitivity, and neuroendocrine circuits. High receptor densities exist in regions important for sensory processing. The main aim of the study was to examine whether intranasal insulin would modulate the activity of areas in charge of olfactory-visual integration. METHODS: As approach, a placebo-controlled double-blind within crossover design was chosen. The experiments were conducted in a research unit of a university hospital. On separate mornings, twenty-six healthy normal-weight males aged between 19 and 31 years received either 40 IU intranasal insulin or placebo vehicle. Subsequently, they underwent 65 min of functional magnetic resonance imaging whilst performing an odor identification task. Functional brain activations of olfactory, visual, and multisensory integration as well as insulin versus placebo were assessed. Regarding the odor identification task, reaction time, accuracy, pleasantness, and intensity measurements were taken to examine the role of integration and treatment. Blood samples were drawn to control for peripheral hormone concentrations. RESULTS: Intranasal insulin administration during olfactory-visual stimulation revealed strong bilateral engagement of frontoinsular cortices, anterior cingulate, prefrontal cortex, mediodorsal thalamus, striatal, and hippocampal regions (p ≤ 0.001 familywise error [FWE] corrected). In addition, the integration contrast showed increased activity in left intraparietal sulcus, left inferior frontal gyrus, left superior frontal gyrus, and left middle frontal gyrus (p ≤ 0.013 FWE corrected). CONCLUSIONS: Intranasal insulin application in lean men led to enhanced activation in multisensory olfactory-visual integration sites and salience hubs which indicates stimuli valuation modulation. This effect can serve as a basis for understanding the connection of intracerebral insulin and olfactory-visual processing.

Authors 4

1. Katja Schumann Aachen Diagnostic and Interventional Neuroradiology

   RWTH Aachen University

   Affiliation as printed

   Diagnostic and Interventional Neuroradiology, RWTH Aachen University, Aachen, Germany

2. Rea Rodriguez‐Raecke Aachen Brain Imaging Facility Interdisciplinary Center for Clinical Research (IZKF) Diagnostic and Interventional Neuroradiology

   RWTH Aachen University

   Affiliation as printed

   Brain Imaging Facility, Interdisciplinary Center for Clinical Research, RWTH Aachen University, Aachen, Germany

   Diagnostic and Interventional Neuroradiology, RWTH Aachen University, Aachen, Germany

3. Rik Sijben Aachen Brain Imaging Facility Interdisciplinary Center for Clinical Research (IZKF)

   RWTH Aachen University

   Affiliation as printed

   Brain Imaging Facility, Interdisciplinary Center for Clinical Research, RWTH Aachen University, Aachen, Germany

4. Jessica Freiherr

   Friedrich-Alexander-Universität Erlangen-Nürnberg · Fraunhofer Institute for Process Engineering and Packaging

   Affiliation as printed

   Department of Psychiatry and Psychotherapy, Friedrich-Alexander, University Erlangen-Nürnberg, Erlangen, Germany

   Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany