# The behavioral functions of upper and lower cortical layers

> **NIH NIH R01** · COLUMBIA UNIVERSITY HEALTH SCIENCES · 2020 · $350,000

## Abstract

PROJECT SUMMARY/ABSTRACT
 The cerebral cortex mediates all of human and animal cognition, encompassing a diverse set of abilities
including sensation, perception, decision making, and motor planning. Dysfunctions of the cerebral cortex are
thought to underlie numerous neurological and psychiatric disorders. A major obstacle both to understanding
normal behaving and to treating pathology is the high degree of complexity of cortical circuitry, which has
remained largely enigmatic. The conventional view of neocortex has been that sensory processing begins in
layer 4 (L4), which was identified a century ago as the principal target of thalamic axons carrying information
from our sensory organs. Sensory transforms are widely believed to occur as excitation spreads serially along
the densest axonal pathways (thalamus→L4→L2/3→L5/6). Recently we discovered that the cerebral cortex,
rather than being a monolithic structure, may contain two entirely separate processing systems, activated by
the same signals arising from the thalamus. L4 is thus not an obligatory distribution hub for cortical activity, and
thalamus activates two distinct “strata” of cortex in parallel.
 This proposal's goal is to identify the behavioral and computational roles of the upper (L2-4) and lower
strata (L5/6) as well as the interactions between them. We will investigate the behavioral roles of these layers
in the mouse whisker system. Specific layers will be optogenetically disrupted in a series of tactile behavioral
tasks, in which task complexity is progressively increased. Interlaminar interactions will also be studied by
recording electrophysiologically from specific layers during behavior and using novel machine learning
techniques designed to identify the type of computation performed in different levels of “deep networks”. The
dimensionality of the representation in a layer will be estimated under normal behaviors and when specific
layers are inactivated.
 Identifying fundamental functions of upper versus cortical layers will likely pave the way for future
studies in other neocortical systems and in higher-order species. Moreover, as the different layers contain
molecularly and biophysically distinct cell types and project to distinct downstream targets, specific
neurological disorders may involve dysfunction of specific pathways, cell types, and layers. Establishing the
behavioral and computational roles of these elements may contribute to development of targeted therapies.

## Key facts

- **NIH application ID:** 9914374
- **Project number:** 5R01NS094659-05
- **Recipient organization:** COLUMBIA UNIVERSITY HEALTH SCIENCES
- **Principal Investigator:** Rui M. Costa
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $350,000
- **Award type:** 5
- **Project period:** 2016-07-15 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9914374

## Citation

> US National Institutes of Health, RePORTER application 9914374, The behavioral functions of upper and lower cortical layers (5R01NS094659-05). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9914374. Licensed CC0.

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