Juxtasomal Biocytin Labeling to Study the Structure-function Relationship of Individual Cortical Neurons

Abstract

The cerebral cortex is characterized by multiple layers and many distinct cell-types that together as a network are responsible for many higher cognitive functions including decision making, sensory-guided behavior or memory. To understand how such intricate neuronal networks perform such tasks, a crucial step is to determine the function (or electrical activity) of individual cell types within the network, preferentially when the animal is performing a relevant cognitive task. Additionally, it is equally important to determine the anatomical structure of the network and the morphological architecture of the individual neurons to allow reverse engineering the cortical network. Technical breakthroughs available today allow recording cellular activity in awake, behaving animals with the valuable option of post hoc identifying the recorded neurons. Here, we demonstrate the juxtasomal biocytin labeling technique, which involves recording action potential spiking in the extracellular (or loosepatch) configuration using conventional patch pipettes. The juxtasomal recording configuration is relatively stable and applicable across behavioral conditions, including anesthetized, sedated, awake head-fixed, and even in the freely moving animal. Thus, this method allows linking cell-type specific action potential spiking during animal behavior to reconstruction of the individual neurons and ultimately, the entire cortical microcircuit. In this video manuscript, we show how individual neurons in the juxtasomal configuration can be labeled with biocytin in the urethane-anaesthetized rat for post hoc identification and morphological reconstruction. Video LinkThe video component of this article can be found at

Functional Architecture and Encoding of Tactile Sensorimotor Behavior in Rat Posterior Parietal Cortex

“…Histology and reconstruction. The histology procedure used to reveal anatomical landmarks and recorded neurons has previously been described (Wong-Riley, 1979;Horikawa and Armstrong, 1988;Narayanan et al, 2014). Briefly, animals were transcardially perfused with 0.1 M PBS, pH 7.2, followed by 4% PFA, and brains were removed and fixed in PFA for 24 h. Twenty-four 100-m-thick tangential sections were obtained, and cytochrome oxidase staining was used on sections 6 -11 to reveal anatomical landmarks in primary somatosensory cortex (S1).…”

“…Either a single or the three most caudal whiskers of the preferred row were spared. Spontaneous activity was recorded for 100 s followed by extracellular current injection to facilitate dye-loading of biocytin (Pinault, 1996;Narayanan et al, 2014). Afterward, neurons were allowed to recover from the filling procedure until prefilling spiking conditions were reestablished (Herfst et al, 2012).…”

Cortical Output Is Gated by Horizontally Projecting Neurons in the Deep Layers

“…Body temperature was maintained at 37.5 ± 0.5 C by a heating pad. Cell-attached recording and labeling was performed as described in detail previously (Narayanan et al, 2014). Briefly, APs were recorded using an extracellular loose patch amplifier (ELC-01X, npi electronic GmbH), and digitized using a CED power1401 data acquisition board (CED, Cambridge Electronic Design, Cambridge, UK).…”

Thalamus drives two complementary input strata of the neocortex in parallel

“…Body temperature was maintained at 37.5 ± 0.5 °C by a heating pad. Cell-attached recording and labeling was performed as described in detail previously 40 . Briefly, APs were recorded using an extracellular loose patch amplifier (ELC-01X, npi electronic GmbH), and digitized using a CED power1401 data acquisition board (CED, Cambridge Electronic Design, Cambridge, UK).…”