Whisker-Based Tactile Object Localization

“Mice (∼2–6 months old, typically males) were deeply anesthetized with 2% isoflurane (by volume in O2; SurgiVet; Smiths Medical) and mounted in a stereotaxic apparatus (Kopf Instruments)”

“During the surgery, the anesthesia levels were adjusted to 1–1.5% to achieve ∼1/second breathing rate in mice”

“The scalp was cleaned with 70% ethanol and betadine. Marcaine (50 µl 0.5% solution) was injected under the scalp for topical anesthesia”

“Ketofen (non-steroidal anti-inflammatory drug, 5 mg/kg) was injected subcutaneously and buprenorphine (opiod analgesic, 0.05 mg/kg) was injected into the intraperitoneal cavity”

“A flap of skin, approximately 1 cm², was removed from the dorsal skull with a single cut. The remaining gelatinous periostium was removed with small scissors”

“The skull was cleaned and dried with sterile cotton swabs. The bone was scraped with a scalpel or slowly turning dental drill for better bonding with the glue”

“The exposed skull was covered with a thin layer of cyanoacrylic glue. The head bar was positioned directly onto the wet glue. Dental acrylic (Jet Repair Acrylic) was added to cover the glue and cement the head bar in position”

“Using a dental drill with an FG 1/4 drill bit, a small hole was drilled into the skull. The virus was introduced using a fine glass injection pipette (tip diameter approximately 15–20 µm) beveled to a sharp tip (outer diameter, 20–30 µm)”

“Following the surgery, buprenorphine (0.1 mg/kg) was administered once. Ketoprofen (5 mg/kg) was administered once a day for two days as an analgesic”

“Animals were examined once a day for three days for signs of infection, lethargy, and grooming”

“Following full and complete recovery from a previous surgery (at least three days post surgery), mice were placed on a water restriction schedule. Mice were housed singly in cages containing tunnels and bedding material, in a reverse light cycle room”

“One ml of water was dispensed manually into bowls which were attached to the inside walls of individual cages, at consistent times of day. Mice consumed this water within minutes”

“All mice undergoing water restriction were monitored daily for hydration, weight, ruffled fur, and movement. If mice drop below 70% of pre-restriction weight, or if mice show signs of dehydration or pain, their health is assessed in more detail”

“After ten days of water restriction, body weight stabilized at approximately 80% of initial weight”

“For head-fixation, the wings of the head bar are seated into notches in a stainless steel holder and fixed with a pair of clamps and thumbscrews. The mouse body is inserted into an acrylic 'body tube' (1⅜ inch i.d.; McMaster; P/N 8486K433)”

“We typically start with the lickport 0.5 mm below the lower lip, and 5 mm posterior to the tip of the nose. During training the lickport typically is moved away from the mouth to discourage compulsive licking”

“Head-fixed mice reported stimuli by licking in go/no-go tasks and also using a forced choice paradigm using a dual lickport. Delay epochs lasting a second or more were used to separate sensation (e.g. tactile exploration) and action (i.e. licking)”

“we have trained head-fixed mice to locate an object (a vertical pole) near their heads with their whiskers. This is by construction an active sensation behavior: mice have to move their whiskers in an intelligent manner to collect information about the world”