The senses of touch, hearing, vision, smell and taste connected to a sculptural brain.

Where Synesthesia Reveals How the Senses Converge

Synesthesia offers a distinctive window into how the brain connects scent, taste, touch, sound and vision. By studying these cross-sensory associations, A&S explores how multisensory integration may shape perception, emotional regulation, behavior, balance, resilience and everyday well-being.

Five Pathways into Human Perception

Each sensory system begins through a distinct biological pathway. These signals do not remain isolated—they interact across cortical, subcortical and association networks to shape integrated perception.

Sensory Signals
Shared Brains
Richer Worlds
Five sensory inputs connect to cortical and subcortical brain networks.

  1. Vision

    Retina · LGN · V1

  2. Audition

    Cochlea · MGN · A1

  3. Olfaction

    Olfactory Epithelium · Olfactory Bulb · Piriform Cortex

  4. Gustation

    Taste Buds · NTS · Insula

  5. Somatosensation

    Skin & Body Receptors · Thalamus · S1/S2

Representative Brain Regions
  • Somatosensory Cortex (S1/S2)
  • Visual Cortex (V1)
  • Auditory Cortex (A1)
  • Insula
  • Brainstem

How the Brain Connects the Senses

Cross-modal integration coordinates sensory signals with attention, salience, memory, emotion and
meaning—transforming separate inputs into an integrated perception.

Conceptual brain network linking sensory convergence, attention, value and emotion.
Cross-Modal
Integration
Network

Sensory Convergence

Thalamus · Superior Temporal
Sulcus (STS) · Posterior Parietal
Cortex / Intraparietal Sulcus (IPS)

Integration, relay and
multisensory convergence

Attention & Salience

Temporoparietal Junction (TPJ) ·
Anterior Cingulate Cortex (ACC)

Salience detection, reorientation
and conscious monitoring

Value & Meaning

Orbitofrontal Cortex (OFC) · Insula

Value, reward, interoception and
cross-modal meaning

Emotion & Memory

Amygdala · Hippocampus

Emotional salience, binding and
episodic memory

Conceptual network view — not an anatomical localization map

Downstream

Potential Bidirectional Neurochemical & Neurotransmitter Modulation

Neurochemical Modulation & Downstream Outcomes

From Synesthetic Mechanisms to Downstream Outcomes

Synesthetic mechanisms may be associated with bidirectional neurochemical modulation. Depending on excitation–inhibition balance,
salience, arousal, context and individual susceptibility, these patterns may support adaptive function or contribute to vulnerability.

Upstream

Potential Neurochemical & Neurotransmitter Modulators

  • Glutamate

    Excitation / Plasticity

  • GABA

    Inhibition / Disinhibition Balance

  • Dopamine

    Reward / Salience / Motivation

  • Serotonin (5-HT)

    Modulation / Stability / Mood

  • Norepinephrine (NE)

    Arousal / Attention / Vigilance

  • Acetylcholine (ACh)

    Attention / Learning

Potential Bidirectional Modulation

Downstream
Woman reflecting in a creative workspace.

Adaptive / Balanced Pattern

Integrated salience · regulated arousal · flexible association

Human Well-Being Outcomes

  • Enhanced Multisensory Encoding & Associative Memory
  • Vivid Imagery, Creativity & Metaphorical Cognition
  • Emotional Resonance & Empathy
  • Perceptual Richness, Salience & Meaning-Making

Potential Human Health Implications

  • Potential Adaptive Benefit
  • Cognitive Resilience / Cognitive Reserve
  • Possible support for healthy cognitive aging.
  • Hypothesis-generating; longitudinal evidence is limited.
Man in a busy public space with his hands at his temples.

Dysregulated / Heightened Pattern

Hyperarousal · reduced inhibition · excessive salience

Potential Vulnerabilities

  • Sensory Overload, Distractibility or Affective Fatigue
  • Anxiety Association
  • OCD Association Less Consistently Replicated

Associations vary across individuals and synesthesia subtypes. Neurochemical roles and causal pathways remain under investigation.

Mechanistic Foundations of Synesthesia and Neuroplasticity

Synesthetic perception may reflect distinctive developmental connectivity and differences in cross-modal feedback and inhibition.
Repeated co-activation may stabilize selected associations and support ongoing network adaptation.

Developmental and Adaptive Determinants

A DNA double helix.

Genetic & Neurodevelopmental
Patterning

Axon guidance · Synapse formation ·
Developmental pruning

A baby looking upward.

Early Sensory Development

Sensory input during critical
developmental periods

A hand playing a piano.

Learning & Contextual Modulation

Associative learning · Repeated
activation · Context

Core Neural Mechanisms

A conceptual illustration of structural connectivity and feedback between brain networks.

Distinctive Structural Connectivity

Retained or atypical cross-modal
connections · altered long-range
connectivity

Functional Disinhibition &
Network Plasticity

Altered feedback · excitation–inhibition
balance · reduced top-down control

From Mechanisms to Adaptive Outcomes

An eye receiving light.

Stable Synesthetic Perception

Automatic and consistent
inducer–concurrent associations

A synaptic connection.

Activity-Dependent Synaptic Reinforcement

Repeated co-activation · association
strengthening · synaptic stabilization

An interconnected neural network.

Adaptive Neuroplasticity

Multisensory network remodeling ·
repeated recruitment · network-level
reorganization

Bidirectional Adaptation

Representative Regions

Parietal Cortex  ·  Hippocampus  ·  Insula  ·  Association Cortex  ·  Occipitotemporal / V4-related Cortex  ·  Prefrontal Cortex

Conceptual framework: proposed mechanisms are supported to different degrees across synesthesia subtypes
and should not be interpreted as a confirmed single causal sequence.

Functional Outcomes and Potential Human Health Implications

Functional Outcomes and Potential Human Health Implications

Synesthetic perception is associated with stable cross-modal binding and distinctive patterns of memory, imagery and flexible association. These functional characteristics may enrich cognition and meaning-making, while broader implications for resilience, cognitive reserve and healthy aging remain preliminary.

Neuroplasticity-Related Functional Outcomes

Associative Memory

Enhanced performance in selected forms of synesthesia

Mental Imagery

Vivid imagery and richer semantic linkage

Creative Flexibility

Flexible cross-modal association and broader meaning

Multisensory Integration

Stable and adaptive integration across sensory channels

Together, these characteristics may support learning, conceptual linkage and flexible cognitive engagement; their expression varies across synesthesia subtypes and individuals.

Potential Relevance to Human Well-Being

Cognitive Enrichment

Memory, imagery and flexible association may support learning, interpretation and meaning-making.

Adaptive Engagement

Stable multisensory integration may support flexible interaction with surroundings and changing contexts.

Emotional and Social Meaning

Cross-modal associations may contribute to emotional resonance and personally meaningful cognition.

Preliminary Human Health Implications

Cognitive Resilience

Potential support for maintaining adaptive cognitive function

Cognitive Reserve

Possible contribution through sustained associative engagement

Healthy Cognitive Aging

Potential reduction in age-related cognitive vulnerability

Evidence Perspective

Functional associations are more consistently reported than long-term health effects.
Evidence varies by synesthesia subtype, study design and sample size.

More consistently supported
functional associationsPreliminary
health hypotheses
Integrating
Neuroscience
for a Brighter
Human Tomorrow

Synesthesia, Neuroplasticity and Dementia

Exploring shared neural processes without implying a confirmed protective or causal relationship.

Synesthetic Processing

Cross-modal brain networks may enable the
blending of sensory information in synesthesia.

Cross-modal connections represented on the brain.

Cross-Activation

Co-activation between inducer-
and concurrent-related sensory regions

Altered Connectivity & Feedback

Distinctive structural connectivity
and differences in inhibitory feedback

Activity-Dependent Neuroplasticity

Repeated cross-modal engagement may drive
lasting changes in neural circuits.

A conceptual synapse with signaling molecules.
  1. Repeated
    Cross-Modal
    Co-activation
  2. Association
    Strengthening &
    Synaptic Adaptation
  3. Learning and
    Memory-Related
    Plasticity
A conceptual protein illustration.

Potential BDNF-Related Pathway

BDNF supports synaptic plasticity, learning and memory. Its possible involvement in synesthesia-related neuroplasticity remains a hypothesis and has not been directly established.

Proposed · Indirect Evidence

Potential Relevance to Cognitive Aging

Shared mechanisms raise important questions about
multisensory processing, cognitive reserve and healthy aging.

An older woman with an illustrative network over the brain.

  • Could sustained associative engagement contribute to cognitive resilience?

  • Could multisensory processing help preserve meaningful interaction and memory support?

  • Could these principles inform non-pharmacological multisensory interventions?

Research questions—not demonstrated effects of synesthesia.

More Established

Cross-activation and distinctive connectivity are supported across synesthesia research.

Hypothesis-Generating

BDNF involvement and cognitive-reserve implications remain unconfirmed.

Clinical Separation

Evidence for multisensory stimulation in dementia does not establish synesthesia as a treatment or preventive factor.

No consistent evidence currently demonstrates elevated BDNF levels in synesthetes or a BDNF-mediated protective effect against dementia.

Dementia, Sensory Decline & Multisensory Intervention
01 · Sensory Pathways

Sensory Decline and Preserved Pathways in Dementia

Sensory changes may accompany cognitive decline, while selected memory and sensory pathways can remain meaningful targets for engagement and supportive care.

Olfactory Decline

An older woman smelling a pink rose.

Potential Early Indicator

Olfactory identification deficits may precede or accompany cognitive impairment along the Alzheimer’s disease continuum.

Smell testing alone is not diagnostic and should be interpreted alongside broader clinical assessment.

Established observation · Not a stand-alone diagnosis

Reminiscence Therapy

An older man and a caregiver looking through a photograph album together.
  • Photographs
  • Life Stories
  • Familiar Objects

Small, Context-Dependent Benefits

Cochrane review: 22 randomized trials · 1,972 participants.

Possible benefits were reported for cognition, communication, quality of life and mood, but effects were generally small and varied by setting and delivery.

Clinically supported · Context-dependent

Relative Preservation of Musical Memory

An older man listening to music through headphones beside a piano.

A Potentially Resilient Memory System

Musical memory can remain relatively preserved even when other memory systems decline.

Familiar music may provide a meaningful cue for memory, emotion, identity and interpersonal engagement.

Evidence supports relative preservation; individual responses vary.

Supported observation

Why These Pathways Matter

Sensory Awareness

Changes in smell and other senses may offer clinically relevant information.

Meaningful Memory Cues

Familiar sensory experiences can support connection and participation.

Foundation for Multisensory Engagement

These observations inform supportive intervention design but do not establish disease modification.

02 · Research to Engagement

From Synesthetic Principles to Multisensory Engagement

A conceptual research bridge connecting cross-modal science with dementia care—without treating synesthesia and multisensory stimulation as equivalent.

Two Distinct Evidence Streams

Synesthesia Research

Cross-activation, distinctive connectivity and stable cross-modal associations.

A woman wearing headphones against a background of colored lights.

Mechanistic insight

Dementia Clinical Context

Sensory decline, altered network integration and neuropsychiatric symptoms.

An older adult looking thoughtfully toward a window.

Clinical context

Conceptually related—not clinically equivalent.

Structured Multisensory Engagement

Combining multiple senses with personally meaningful experiences.

  • Vision
  • Sound
  • Scent
  • Touch
  • Personally Meaningful Memory Cues

Potential Functional Pathway

  1. Engagement and Attention

    Increased attention, motivation and participation.

  2. Behavioral and Affective Regulation

    Potential reduction in agitation, apathy and depressive symptoms.

  3. Selected Cognitive Support

    Potential modest improvement in cognitive function.

  4. Potential Adaptive Plasticity

    Repeated engagement may support functional adaptation; rewiring, recovery and disease modification are not established.

03 · Clinical Evidence

Clinical Evidence: Multisensory Stimulation in Dementia

Randomized-trial evidence suggests benefits for selected neuropsychiatric and cognitive outcomes, while important limitations remain.

An older woman holding a textured sensory ball with a caregiver, a soft light, scent diffuser and music nearby.

Structured Multisensory Stimulation

Controlled combinations of visual, auditory, olfactory and tactile cues.

  • Vision
  • Sound
  • Scent
  • Touch
  • Interaction

2025 Meta-Analysis

16 studies · 974 participants · Random-effects model

Effect sizes for multisensory stimulation in dementia
OutcomeHedges g95% CI
Agitation−0.96−1.44 to −0.48
Apathy−1.27−2.08 to −0.46
Depression−0.28−0.48 to −0.07
Overall cognition+0.30+0.09 to +0.52
Anxiety−0.81−1.79 to +0.17

Negative values favor reduction of symptoms; positive values favor improvement in cognition. CI = confidence interval.

Supported or Promising

  • Reduced agitation
  • Reduced apathy
  • Reduced depressive symptoms
  • Modest improvement in overall cognition
  • Greater engagement and meaningful interaction

Clinically supported · Context-dependent

Not Established

  • Prevention or reversal of dementia
  • Disease-modifying treatment
  • Synesthesia as a clinical therapy
  • Neuroplastic rewiring or recovery
  • BDNF-mediated protection

Hypothesis-generating or unsupported

How to Interpret the Evidence

Clinical Role

Potential non-pharmacological adjunct.

Evidence Limitation

Protocols, populations and several outcomes were heterogeneous.

Conceptual Boundary

MSS evidence does not demonstrate that synesthesia prevents or treats dementia.