By Harshit
CAMBRIDGE, MASSACHUSETTS, NOV. 30 —
For decades, scientists viewed vision as a primarily bottom-up process: light hits the retina, signals travel to the visual cortex, and the brain forms an image. New research from MIT’s Picower Institute, published in Neuron, fundamentally challenges this model, showing the relationship is a two-way street.
The study, led by senior author Professor Mriganka Sur, demonstrates that the brain’s executive control center—the prefrontal cortex—sends highly tailored and opposing signals to visual processing regions. These signals essentially tune the visual system, adjusting what an animal sees based on its internal state (arousal or alertness) and current behavior (moving or still).
The major finding is that the brain uses specialized feedback—customized signals—rather than global modulation (one general broadcast) to influence perception and action.
1. The Discovery: Targeted Control, Not Global Broadcast
The prefrontal cortex (PFC) has long been viewed as the brain’s control tower, responsible for planning, decision-making, and focus. But the MIT team asked a deeper question: Does the PFC send one sweeping message, or multiple highly specialized instructions?
Using mice as a model, researchers focused on two key subregions of the PFC:
- Orbitofrontal Cortex (ORB): Associated with decision-making and reward evaluation.
- Anterior Cingulate Area (ACA): Known for roles in attention, conflict monitoring, and error detection.
They discovered that these areas do not broadcast a single uniform message. Instead, they send distinct, tailored signals to two major target regions:
- Primary Visual Cortex (VISp) — responsible for initial visual processing.
- Primary Motor Cortex (MOp) — responsible for controlling movement.
This supports the study’s central thesis:
“There are targeted projections for targeted impact.”
2. The Opposing Forces: How Mood and Alertness Tune Vision
A striking insight from the research is how the ACA and ORB shape visual perception in opposite ways depending on arousal levels.
A. ACA: Enhancing Clarity Under Rising Arousal
The ACA acts like a visual sharpening tool.
- Role: Its activity rises alongside arousal.
- Impact on VISp: It sharpens visual representations, making important details clearer when the animal becomes more alert.
This likely helps the brain focus more intensely when something in the environment becomes meaningful.
B. ORB: Dampening Strong or Distracting Stimuli
The ORB acts like a visual volume-dampener, stepping in only during high stress.
- Role: Kicks in only when arousal crosses a high threshold.
- Impact on VISp: It decreases the clarity of visual encoding, reducing overwhelming or distracting signals.
Lead author Sofie Ährlund-Richter said the two regions act like “balancing forces,” with the ACA enhancing uncertain stimuli and the ORB dampening overly strong ones.
3. Action vs. Perception: The Role of Movement
The study also explored how ACA and ORB communicate differently with motor vs. visual regions.
Signals Sent to the Motor Cortex (MOp)
- Carried detailed information about running speed.
- Helps coordinate movement with precise intensity.
Signals Sent to the Visual Cortex (VISp)
- Carried only a binary signal—moving or still.
- This minimal cue triggers a fundamental visual state shift, stabilizing perception during movement.
This demonstrates that the PFC tailors each message based on the destination and its functional role.
4. Mapping the Circuits: Anatomy of Specialized Control
To understand how the PFC exerts such precise influence, researchers conducted anatomical circuit tracing and neural recordings using mice running on a wheel while exposed to visual stimuli.
Key anatomical findings include:
Cellular Specificity
Both ACA and ORB connect to a wide spectrum of cell types, revealing a highly complex command network.
Layer Specificity
The feedback was not random—it followed precise cortical layering:
- ACA targeted Layer 6 of VISp, a layer associated with feedback control and regulatory signals.
- ORB targeted Layer 5 of VISp, a major output layer linked to deeper processing and motor-linked pathways.
These differing targets imply they influence entirely different stages of visual computation.
Conclusion
The findings challenge the classical view of the brain as a set of separate, passive processing modules. Instead, they support a model where the prefrontal cortex actively sculpts sensory and motor information, rewriting what the animal sees based on mood, behavior, and internal state.
The study reveals a dynamic relationship between perception and action—where vision doesn’t merely guide behavior, but behavior and internal state continuously guide vision.