title: Emotion modulation of the startle reflex in essential tremor: Blunted reactivity to unpleasant and pleasant pictures.
abstract: Essential tremor is a highly prevalent movement disorder characterized by kinetic tremor and mild cognitive-executive changes. These features are commonly attributed to abnormal cerebellar changes, resulting in disruption of cerebellar-thalamo-cortical networks. Less attention has been paid to alterations in basic emotion processing in essential tremor, despite known cerebellar-limbic interconnectivity.
  
  
  
  In the current study, we tested the hypothesis that a psychophysiologic index of emotional reactivity, the emotion modulated startle reflex, would be muted in individuals with essential tremor relative to controls.
  
  
  
  Participants included 19 essential tremor patients and 18 controls, who viewed standard sets of unpleasant, pleasant, and neutral pictures for six seconds each. During picture viewing, white noise bursts were binaurally presented to elicit startle eyeblinks measured over the orbicularis oculi.
  
  
  
  Consistent with past literature, controls' startle eyeblink responses were modulated according to picture valence (unpleasant > neutral > pleasant). In essential tremor participants, startle eyeblinks were not modulated by emotion. This modulation failure was not due to medication effects, nor was it due to abnormal appraisal of emotional picture content.
  
  
  
  Neuroanatomically, it remains unclear whether diminished startle modulation in essential tremor is secondary to aberrant cerebellar input to the amygdala, which is involved in priming the startle response in emotional contexts, or due to more direct disruption between the cerebellum and brainstem startle circuitry. If the former is correct, these findings may be the first to reveal dysregulation of emotional networks in essential tremor.
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA. Electronic address: jlafo@phhp.ufl.edu.
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Lafo
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA; Institute for Regenerative Medicine, University of Zurich, Center for Prevention and Dementia Therapy, Wagistrasse 14, 8952 Schileren, Switzerland. Electronic address: mikos.ania@gmail.com.
authors.forename: Ania
authors.initials: A
authors.lastname: Mikos
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA. Electronic address: pmangal@phhp.ufl.edu.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Mangal
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA. Electronic address: bonnie.m.scott@phhp.ufl.edu.
authors.forename: Bonnie M
authors.initials: BM
authors.lastname: Scott
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA. Electronic address: etrif07@phhp.ufl.edu.
authors.forename: Erin
authors.initials: E
authors.lastname: Trifilio
authors.affiliation: Department of Neurology, University of Florida College of Medicine, University of Florida, HSC Box 100236, Gainesville, FL 32610-0236, USA. Electronic address: okun@neurology.ufl.edu.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Okun
authors.affiliation: Department of Clinical and Health Psychology, College of Public Health & Health Professions, University of Florida, PO Box 100165, Gainesville, FL 32610-0165, USA; Department of Neurology, University of Florida College of Medicine, University of Florida, HSC Box 100236, Gainesville, FL 32610-0236, USA. Electronic address: dawnbowers@phhp.ufl.edu.
authors.forename: Dawn
authors.initials: D
authors.lastname: Bowers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001288:Attention; D001767:Blinking; D004576:Electromyography; D004644:Emotions / Q000502:physiology*; D020329:Essential Tremor / Q000503:physiopathology* / Q000523:psychology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D013216:Reflex, Startle / Q000502:physiology*
keywords: Amygdala; Cerebellum; Emotion; Essential tremor; Startle