Intracranial Self-Stimulation

Abstract

Rats, and many other vertebrates, will work to deliver electrical pulse trains to certain brain loci via depth electrodes --a phenomenon known as intracranial self--s-mula-on (ICSS). The effect of the electrical sBmulaBon that leads the animal to seek and reiniBate the sBmulaBon is called brain s-mula-on reward (BSR) and is related to the effects of naturally rewarding sBmuli. For example, BSR can compete with, summate with, and subsBtute for, the rewarding effects of natural goal objects such as food and water. However, unlike behavior maintained by natural rewards, the behavior controlled by BSR remains stable between and within sessions. This is due to the fact that the signal is injected directly into the brain, thus bypassing sensory adaptaBon and physiological feedback mechanisms that discount natural rewards. In addiBon, response--reinforcement delays that degrade natural rewards are minimized. Given that the electrically induced rewarding effect originates as a volley of observable acBon potenBals in axons coursing past idenBfiable CNS sites, the phenomenon of BSR has long been regarded as a gateway to tracing the neural circuitry involved in the pursuit of natural rewards. It has also been proposed that dependence--inducing drugs gain their grip over behavior, at least in part, due to their ability to alter neurotransmission in the circuitry underlying BSR.Preliminaries: measuring pharmachological effects on BSR: In early studies, the effects of drugs on BSR were inferred from changes in the rate of lever pressing. This pracBce was based on the intuiBve assumpBon that the vigor of instrumental performance should reflect the strength of the rewarding effect. One problem with this assumpBon is that response tempo depends on mulBple variables and can thus vary even when the intensity of the rewarding effect is constant. Another is that the magnitude of the change in response rate produced by a drug--induced change in reward intensity depends on the baseline rate and does so in a highly non--linear manner.An iniBal challenge to the rate measure was posed by the finding that rats preferred higher-current to lower----current sBmulaBon despite the fact that lower response rates were obtained when Intracranial Self-Stimulation Shizgal & Hernandez

Intracranial Self-Stimulation to Evaluate Abuse Potential of Drugs

“…Second, electrical parameters of stimulation frequency and amplitude were manipulated at single or multiple electrode sites to gain information about the conduction velocity, refractory periods, and connectivity patterns of neurons mediating ICSS (Stellar and Stellar, 1985;Shizgal and Murry, 1989;Yeomans, 1989). These studies implicated low-threshold myelinated neurons as the likely substrate, and these studies also identified multiple parallel networks of neurons capable of supporting ICSS.…”

The cognitive basis of intracranial self-stimulation of midbrain dopamine neurons

“…The finding that many species, including humans, will work to receive stimulation of various brain regions has been taken as evidence that those regions encode natural rewards or pleasure 5,6,8,10 . Regions that support ICSS predominantly rest across the medial forebrain bundle, but can also be found in many parts of the limbic and extrapyramidal motor systems 1, [10][11][12][13] . The use of this paradigm for studying the neural substrates of reward has increased considerably in the last decade, afforded in part by the optogenetic revolution that allows for incredibly precise control over neuronal activity in rodents [14][15][16][17][18] .…”