Academic journal article Cognitive, Affective and Behavioral Neuroscience

Limb-Specific Emotional Modulation of Cervical Spinal Cord Neurons

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Limb-Specific Emotional Modulation of Cervical Spinal Cord Neurons

Article excerpt

Abstract Emotional stimuli receive prioritized attentional and motoric processing in the brain. Recent data have indicat- ed that emotional stimuli enhance activity in the cervical spinal cord as well. In the present study, we used fMRI to investigate the specificity of this emotion-dependent spinal cord activity. We examined whether the limb depicted in a passively viewed image (upper vs. lower) differentially influenced activity in the cervical segments that innervate the upper limbs, and whether this effect was enhanced by emotion. Participants completed four fMRI runs: neutral-up- per limb, neutral-lower limb, negative-upper limb, and neg- ative-lower limb. The results indicated main effects of limb and emotion, with upper limbs and negative stimuli eliciting greater activity than lower limbs and neutral stimuli, respec- tively. For upper-limb runs, negative stimuli evoked more activity than did neutral stimuli. Additionally, negative stimuli depicting upper limbs produced stronger responses than did negative stimuli depicting lower limbs. These results suggest that emotional stimuli augment limb-specific responses in the spinal cord.

Keywords Cervical spinal cord . Emotion . Functional MRI . Spinal fMRI . Emotion-movement interactions

Emotions facilitate the execution of motoric responses (Koganemaru, Domen, Fukuyama, & Mima, 2012), allowing an individual to approach or avoid salient stimuli (e.g., Davidson & Irwin, 1999). Recent neuroimaging data have allowed researchers to delineate many of the neural substrates underlying this emotional modulation of movement. Multiple studies have detected increased responsivity in the supplemen- tary motor area during the perception of emotionally arousing stimuli (e.g., Oliveri et al., 2003; Schienle, Schäfer, Walter, Stark, & Vaitl, 2005), particularly when an ongoing movement is interrupted by an emotional stimulus (Sagaspe, Schwartz, & Vuilleumier, 2011). Pereira et al. (2010) also noted that the midcingulate cortex is involved in the integration of the per- ception of negatively valenced emotional information and the performance of movements. These results have been complemented by functional connectivity analyses indicating that fear-relevant stimuli increase the connectivity between the amygdala and both the inferior occipital gyrus and the premotor cortex, suggesting a functional link between the structures related to fear, perception, and movement (Tettamanti et al., 2012). Additionally, studies utilizing transcranial magnetic stimulation (TMS) have consistently noted increased sensitivity in the motor cortex during emotional perception, suggesting an increase in the excitability of the corticospinal tract (Coelho, Lipp, Marinovic, Wallis, & Riek, 2010; Coombes at al., 2009; Hajcak et al., 2007; Schutter, Hofman, & Van Honk, 2008;van Loon, van den Wildenberg, van Stegeren, Hajcak, & Ridderinkhof, 2010). Together, these studies provide insights into the brain regions involved in emotion-movement interac- tions. However, to date, little research has examined the role of the spinal cord in these emotion-dependent responses, despite the fact that this structure is the neuroanatomical link between the nervous system regions involved in the planning and exe- cution of these movements.

The emotional modulation of spinal cord activity was re- cently investigated in a study utilizing functional magnetic resonance imaging (fMRI) of the spinal cord. Smith and Kornelsen (2011) imaged the cervical spinal cord during the presentation of emotionally negative (threatening and/or gory), positive (erotic), or neutral (landscape or cityscape) photographs. For half of the trials, the participants were instructed to make buttonpress responses to the images, indi- cating whether the depicted scene was indoors or outdoors. Other trials required only passive viewing of the images (i.e., no motoric response). The results showed that negative stimuli evoked greater activity in cervical spinal cord segments C5-C8 than did positive or neutral stimuli. …

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