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A predictive reinforcement model of dopamine neurons for learning approach behavior.

A neural network model of how dopamine and prefrontal cortex activity guides short- and long-term information processing within the cortico-striatal circuits during reward-related learning of approach behavior is proposed. The model predicts two types of reward-related neuronal responses generated during learning: (1) cell activity signaling errors in the prediction of the expected time of reward delivery and (2) neural activations coding for errors in the prediction of the amount and type of reward or stimulus expectancies. The former type of signal is consistent with the responses of dopaminergic neurons, while the latter signal is consistent with reward expectancy responses reported in the prefrontal cortex. It is shown that a neural network architecture that satisfies the design principles of the adaptive resonance theory of Carpenter and Grossberg (1987) can account for the dopamine responses to novelty, generalization, and discrimination of appetitive and aversive stimuli. These hypotheses are scrutinized via simulations of the model in relation to the delivery of free food outside a task, the timed contingent delivery of appetitive and aversive stimuli, and an asymmetric, instructed delay response task.

Animals↗
PubMed2001

Impairments in visual discrimination learning and recognition memory produced by neurotoxic lesions of rhinal cortex in rhesus monkeys.

Much work on the cognitive functions of the primate rhinal (i.e. entorhinal plus perirhinal) cortex has been based on aspiration lesions of this structure, which might disrupt fibres passing nearby and through the rhinal cortex in addition to removing the cell bodies of the rhinal cortex itself. To determine whether damage limited to the cell bodies of the rhinal cortex is sufficient to impair visual learning and memory, four rhesus monkeys (Macaca mulatta) were preoperatively trained on a battery of visual learning and memory tasks, including single-pair discrimination learning for primary reinforcement, single-pair discrimination reversals, concurrent discrimination learning and reversal, and delayed matching-to-sample. Following acquisition of these tasks and a preoperative performance test, ibotenic acid was injected bilaterally into the rhinal cortex, and the monkeys were retested. Consistent with the results of studies using aspiration lesions, the monkeys were impaired on single-pair discrimination learning as well as recognition memory performance postoperatively, although reliable reversal learning impairments were not observed. The magnitude of postoperative impairment in discrimination learning was not correlated with the magnitude of postoperative impairment in recognition memory, suggesting a possible dissociation between these functions within the rhinal cortex. The correspondence of behavioural deficits following aspiration and neurotoxic lesions of the rhinal cortex validates the attribution of various cognitive functions to this structure, based on the results of studies with aspiration lesions.

Animals↗
PubMed1984

Effects of task-irrelevant cues and reinforcement delay on choice-escape learning following inescapable shock: evidence for a deficit in selective attention.

Prior exposure to inescapable shock has been reported to interfere with choice-escape learning, but several investigators have failed to obtain this effect. A series of five experiments examined the conditions under which choice-escape learning in an automated Y-maze is impaired by pretreatment with inescapable shock. Inescapably shocked rats made more errors and responded more slowly than did controls only when shock termination was delayed and task-irrelevant cues were present during choice-escape training. These findings are discussed in terms of information processing and neurochemical consequences of exposure to inescapable shock.

Animals↗
PubMed2006

Evaluation of the sustained implementation of a mental health learning initiative in long-term care.

BACKGROUND: This paper describes an innovative education program for the management of mental health problems in long-term care (LTC) homes and the evaluation of its longer-term sustainability. Since 1998, the "Putting the P.I.E.C.E.S. Together" learning initiative has been providing education sessions and related learning strategies aimed at developing the knowledge and skills of health professionals who care for older persons with complex physical and mental health needs and associated behaviors, in Ontario, Canada. A major focus of this province-wide initiative was the development of in-house Psychogeriatric Resource Persons (PRPs). Evaluation of this initiative included the completion of pre- and post-education questionnaires (over three data collection time periods) assessing learner confidence (N = 1,024 and 792, for pre- and post-education, respectively) and session evaluation questionnaires gathering feedback on the session (N = 2,029 across all sessions). A survey of LTC homes in Ontario (N = 439, 79% of the homes in the province) was conducted to assess longer-term sustainability. RESULTS: Ratings of the sessions indicated that they were relevant to learners' clinical practice. There were significant increases in ratings of ability to recognize and understand challenging behaviors and mental health problems, and in ability to use a variety of assessment tools. Few homes (15%) do not have a PRP; over 50% of the staff who completed the first session in 1999 continue to serve as a PRP and to apply learned skills. CONCLUSIONS: A learning initiative with supportive and reinforcing strategies can develop in-house PRPs to enhance the care of the elderly in LTC. Incorporation of PRP functions into job descriptions and management support contributed to the success of this initiative. This study highlights the importance of work environments that support and reinforce the use of learned skills to the success of continuing education and quality improvement initiatives in LTC.

Aged↗
PubMed2005

Some decks are better than others: the effect of reinforcer type and task instructions on learning in the Iowa Gambling Task.

The Iowa Gambling Task (Bechara, Damasio, Damasio, & Anderson, 1994) has become widely used as a laboratory test of "real-life" decision-making. However, aspects of its administration that have been varied by researchers may differentially affect performance and the conclusions researchers can draw. Some researchers have used facsimile money reinforcers while others have used real money reinforcers. More importantly, the instructions participants receive have also been varied. While no differences have been reported in performance dependent on reinforcer type, no previous comparison of participants' instructions has been conducted. This is despite one set of instructions giving participants a clear hint about the nature of the task. Additionally, in previous research one set of instructions have not been used exclusively with one reinforcer type making any differential or cumulative effects of these factors difficult to interpret. The present study compared the effects of instruction and reinforcer type on IGT performance. When participants received instructions without a hint performance was affected by reinforcer type. This was not the case when the instructions included a hint. In a second IGT session performance was improved in participants who had received the hint instructions compared with those who had not.

Analysis of Variance↗
PubMed2005

Dynamics of learning in coupled oscillators tutored with delayed reinforcements.

In this work we analyze the solutions of a simple system of coupled phase oscillators in which the connectivity is learned dynamically. The model is inspired by the process of learning of birdsongs by oscine birds. An oscillator acts as the generator of a basic rhythm and drives slave oscillators which are responsible for different motor actions. The driving signal arrives at each driven oscillator through two different pathways. One of them is a direct pathway. The other one is a reinforcement pathway, through which the signal arrives delayed. The coupling coefficients between the driving oscillator and the slave ones evolve in time following a Hebbian-like rule. We discuss the conditions under which a driven oscillator is capable of learning to lock to the driver. The resulting phase difference and connectivity are a function of the delay of the reinforcement. Around some specific delays, the system is capable of generating dramatic changes in the phase difference between the driver and the driven systems. We discuss the dynamical mechanism responsible for this effect and possible applications of this learning scheme.

Animals↗
PubMed2004

Ventral striatal control of appetitive motivation: role in ingestive behavior and reward-related learning.

The nucleus accumbens is a brain region that participates in the control of behaviors related to natural reinforcers, such as ingestion, sexual behavior, incentive and instrumental learning, and that also plays a role in addictive processes. This paper comprises a review of work from our laboratory that focuses on two main research areas: (i). the role of the nucleus accumbens in food motivation, and (ii). its putative functions in cellular plasticity underlying appetitive learning. First, work within a number of different behavioral paradigms has shown that accumbens neurochemical systems play specific and dissociable roles in different aspects of food seeking and food intake, and part of this function depends on integration with the lateral hypothalamus and amygdala. We propose that the nucleus accumbens integrates information related to cognitive, sensory, and emotional processing with hypothalamic mechanisms mediating energy balance. This system as a whole enables complex hierarchical control of adaptive ingestive behavior. Regarding the second research area, our studies examining acquisition of lever-pressing for food in rats have shown that activation of glutamate N-methyl-d-aspartate (NMDA) receptors, within broadly distributed but interconnected regions (nucleus accumbens core, posterior striatum, prefrontal cortex, basolateral and central amygdala), is critical for such learning to occur. This receptor stimulation triggers intracellular cascades that involve protein phosphorylation and new protein synthesis. It is hypothesized that activity in this distributed network (including D1 receptor activity) computes coincident events and thus enhances the probability that temporally related actions and events (e.g. lever pressing and delivery of reward) become associated. Such basic mechanisms of plasticity within this reinforcement learning network also appear to be profoundly affected in addiction.

Animals↗
PubMed1996

Assessing sensory capacity of animals using operant technology.

Operant technology is often employed in farm management (e.g., waterers in which an animal pushes a valve with its nose or snout [response] to receive water [reinforcement]). An animal learns when successive approximations to the desired response are reinforced, thereby establishing the operant behavior (shaping). Animals are challenged by schedules of reinforcement that increase level of operant response. The method has been used to obtain quantitative measures of preference for prepared feeds, flavors, and harvest methods and feed processing. Basic information on what an animal sees in terms of color, patterns, and illumination are cited. Innovative research on animals' ability to smell and to hear are reviewed. Studies on regulation of environmental conditions by the animals themselves through operant methods will contribute to needed knowledge about animal welfare. Several examples of these studies are included in this review. Results of numerous studies indicate that operant technology can be a powerful tool to assess the sensory capacity of animals.

Animal Welfare↗