Are You Blind and Deaf to Your Feelings?

(Posted on Saturday, April 27, 2024)

KEY POINTS

• The brain’s emotional responses persist without sight or sound, illuminating innate processing.

• Plasticity in the brain allows it to adapt to sensory deprivation.

• The study results can inform interventions for sensory impairments.

Humans rely on the five senses to make sense of the world around us, including understanding our feelings and the feelings of others. But what if you do not have access to your senses? How do those who are blind or deaf organize sensory cues and create emotional responses? A recent study conducted by a team of researchers at the Social and Affective Neuroscience Group at IMT School for Advanced Studies in Lucca, Italy, found that our brain is wired to generate emotional meaning, even when we cannot see or hear. Our feelings are so powerful that even if you are blind and deaf, your brain can generate intense emotional responses.

Role of Sensory Inputs in Emotional Processing

The five senses play an important role in emotional processing, learning, and interpretation. Vision is dominant, with the visual cortex playing a vital role in identifying emotions and helping us navigate our own emotions and those of others. Audio stimuli also impact emotional processing, with examples such as beautiful music sparking joy or noisy environments causing frustration.

Emotions can also be influenced by our sense of taste and smell, with flavors and odors being linked to emotional memory recall. There are even imperceptible influences of human senses on emotion, like human chemosignals influencing behavior. Understanding how the senses impact emotion provides interesting insights into the wonders of the human brain and the significant impacts on behavior.

Investigating the Neural Representation of Emotional Experiences

The study conducted by the researchers at the Social and Affective Neuroscience Group and led by Giada Lettieri investigated how the brain’s processing and interpretation of sensory input influences the neural representation of emotional experiences. Using functional magnetic resonance imaging, the research team examined brain activity in 50 deaf and blind as well as typically developed participants while exposing them to an emotional movie either in sound and visual, just sound, or just visual conditions.

The researchers also included a cohort of 124 independent participants who were asked to watch the same movie and track their emotional experiences outside of the brain scanner. This was done with the aim of predicting how the brain reacts to emotions such as amusement, fear, and sadness in individuals with and without sensory deprivation.

Findings: Insights Into the Brain’s Response to Emotional Stimuli

Various important findings show that emotions are represented in the brain regardless of sensory experience and modalities. Firstly, the ventromedial prefrontal cortex was found to represent emotion categories regardless of the brain’s interpretation of the input or the sensory channel or receptor type that was stimulated. This region stored an abstract representation of emotion categories and showed consistent activity patterns for specific emotions like love or contempt across individuals with and without sensory deprivation.

Secondly, the activity of the posterior portion of the superior temporal cortex was decoded to track changes in emotional valence, meaning whether the emotion was determined to be good or bad, even in individuals lacking visual or auditory inputs since birth. However, the sensory experience affected how emotions were stored in the posterior portion of the superior temporal cortex, the back part of the brain, indicating that our senses help shape how emotions are represented.

Furthermore, regions like the mid-cingulate cortex, insula, somatomotor cortex, thalamus, hypothalamus, and caudate nucleus were better explained by affective dimensions like valence and arousal than by sensory input. The primary sensory areas preferentially represented emotions based on modality, with blind individuals showing higher fitting values in the early auditory cortex when exposed to auditory stimuli and deaf individuals showing higher fitting values in early visual areas when exposed to visual stimuli. This suggests that in the absence of input from one of the senses, the brain’s primary sensory areas become more specialized and responsive to emotional information conveyed through the remaining intact senses. This reflects the brain’s plasticity and ability to adapt to sensory deprivation.

The study showed that language plays a part in processing emotions, indicating that how we understand emotions in the ventromedial prefrontal cortex, the front part of the brain, might depend on word meanings. Also, they discovered that emotions are grouped in clear categories in one part of the brain, the ventromedial prefrontal cortex, and are more varied in another part, the left posterior portion of the superior temporal gyrus.

Beyond these findings, the study indicates that sensory experience, in general, rather than the specific sense itself, plays a significant role in how the brain organizes emotional information. Higher-order occipital regions encoded emotion categories similarly in sensory-deprived and typically developed individuals, suggesting that the brain constructs a framework for emotional representation independently of sensory experience. However, sensory inputs during development shape its functioning. Finally, the study acknowledged some limitations, including the small sample size, lack of affective ratings from congenitally blind and deaf participants, and the challenge of capturing real-time emotion reports in blind individuals. Despite these limitations, the study provided valuable insights into the neural representation of emotional experiences across sensory and modal domains.

Future Directions

Exploring the clinical implications of these findings could inform interventions and therapies for individuals with sensory impairments as well as those seeking to manage behaviors. Comparing the neural representations of emotions across different cultural backgrounds could provide insights into the universality versus cultural specificity of emotional processing. Exploring how cultural factors interact with sensory inputs to shape emotional experiences could enrich our understanding of emotional diversity.

Additionally, advanced neuroimaging techniques like electroencephalography or functional near-infrared spectroscopy could offer complimentary insights into the neural mechanisms underlying emotional processing, providing more data in a wider range of populations. This study sheds a hopeful light on our innate ability to navigate the world, even in the absence of certain sensory inputs, and provides an exciting foundation for future studies.

Read the article online on Psychology Today.