Developing novel approaches to study and treat interoceptive fear

Key to understanding interoceptive fear is the development of novel approaches that can safely and reliably enhance awareness for cardiorespiratory sensations – the primary driver of interoceptive fear. In addition to studying various forms of CO₂ modulation, Dr. Feinstein and his close collaborator, Dr. Sahib Khalsa, have employed isoproterenol, a rapid-acting peripheral β-adrenergic agonist akin to adrenaline.  Through intravenous administration of isoproterenol to rare lesion patients, as well as patients with high levels of anxiety sensitivity undergoing functional neuroimaging, they have begun to parse the neural systems of cardiorespiratory awareness.  Since most interoceptive perturbations entail sympathetically-mediated autonomic changes, Dr. Feinstein and Dr. Khalsa have also taken a deep dive into the other end of the autonomic spectrum by studying Floatation-REST (Reduced Environmental Stimulation Therapy), a novel intervention that allows the nervous system to enter a relaxed/parasympathetic physiological state by systematically reducing sensory stimulation from the external world.  They recently received the first NIH-funded grant to explore Floatation-REST and have several ongoing clinical trials examining the long-term effects of floating in anxious populations.  Their research has shown that Floatation-REST is not a form of sensory deprivation (a common misnomer), but instead, the float environment actually enhances one’s awareness for cardiorespiratory sensations.  The practice of mindful meditation is often predicated on focusing one’s full attention and awareness on present moment sensations such as the breath, and consequently, the float environment was found to spontaneously induce states of mindfulness, including in anxious patients who often have great difficulty meditating.  Moreover, the float environment appeared to weaken the bond between cardiorespiratory sensations and anxiety, especially when such sensations were experienced against a backdrop of reduced muscle tension and physiological relaxation.  This form of reciprocal inhibition has the potential to greatly reduce anxiety sensitivity and help anxious patients (including those with PTSD) form a new association in their brain, one that links the experience of cardiorespiratory sensations with a state of relaxation instead of anxiety.

Understanding the temporal dynamics of emotion and feeling

Starting with his first publication, Dr. Feinstein has been interested in understanding the temporal dynamics of emotional processing in the human brain, especially as it relates to habituation and the recovery of emotion.  As part of this program of research, he asked the following question:  Can the experience of an emotion persist once the memory for what induced that emotion has been forgotten?  In order to answer this question, he studied a rare group of patients with severe anterograde amnesia following circumscribed bilateral damage to the hippocampus.  The results revealed a striking dissociation between the conscious awareness of an emotional state and the conscious recollection for that state’s origin.  Even though the amnesic patients could no longer remember watching a series of emotional film clips when queried 5 minutes after they were over, the induced feelings of emotion persevered for over 30 minutes.  These findings suggest that the brain is organized in such a way that a feeling of emotion can persist without any explicit memory for its cause.  Quite strikingly, the feeling of sadness persisted longer in the amnesic patients than the comparison subjects (whose memory for the film clips was entirely intact).  The findings have since been replicated in patients with Alzheimer's disease and have important implications for how society treats individuals with memory disorders, as events that have long been forgotten could continue to induce suffering or well-being.  Following up on this line of research, Dr. Feinstein’s doctoral dissertation explored the brain regions necessary for holding onto an emotional state.  In a large sample of lesion patients with damage to different regions of the limbic and paralimbic system, it was discovered that patients with bilateral damage affecting both the amygdala and insula experienced extremely transient states of emotion that would rapidly dissipate within a minute.  This research suggests that the amygdala and insula play a critical role in holding onto states of emotion, while the ventromedial prefrontal cortex and hippocampus serve to regulate these states.  Importantly, dysfunction within this larger circuitry may contribute to the prolonged periods of emotional suffering inherent to conditions like anxiety and depression.

Dr. Feinstein’s Curriculum Vitae

Dr. Feinstein’s research has also been featured in the following books