Francisco Gonzalez-Lima - US grants

The long-term goal is to localize the neural structures involved in associative learning of auditory signals. Experiments with 2- deoxyglucose (2-DG) techniques have been designed to functionally map the neural metabolic activity related to the specific components involved in auditory conditioning, namely auditory conditioned stimulus (CS), unconditioned stimulus reinforcers (US), and conditioned responses (CR). Are the learned properties of a sound differentially represented at various levels of the auditory pathway? Which are the brain structures related to attentional and learning processes involved in associative learning? Two experimental protocols have been designed to address these questions using a combination of classical and operant conditioning paradigms in conjunction with autoradiographic 2-DG techniques for the study of behavior in freely moving animals. The basic idea is to quantitate the uptake of 2-DG in the brain of rats during a variety of different behavioral conditioning and control situations. The proposed experiments manipulate the specific components involved in auditory conditioning (CS, US, CR) in an effort to discriminate the neural representation, in terms of 2-DG uptake, of these components independently or combined in paired and unpaired trials. In the first protocol two CSs will be compared, using a differential paradigm with reinforced (CS+) and nonreinforced (CS-) presentations, in order to discriminate the tonotopic from the reinforcing effects of CSs in terms of 2-DG uptake. The 2- DG method provides a tool that allows simultaneous visualization of tonotopic representation and functional activity in the auditory system. This method will be used also in a second protocol comparing the effects of identical CS-US pairings on the brains of four groups of rats: performing animals trained to bar press for reward during a sound signal (discriminative group), or bar pressing regardless of sound (nondiscriminative group), and rats yoked to the above groups and subjected to paired CS-US (classical group) and unpaired CS-US (control group), respectively. It is expected that comparisons using complementary stimulus- response conditions will serve to elucidate the neuroanatomical structures related to the specific components involved in auditory conditioning. The most important outcome of the proposed research would be the identification and functional mapping of rat brain structures responsible for the associative learning and memory of auditory stimuli.

The long-term goal is to localize the neural structures involved in associative learning of auditory signals. Experiments with 2- deoxyglucose (2-DG) techniques have been designed to functionally map the neural metabolic activity related to the specific components involved in auditory conditioning, namely auditory conditioned stimulus (CS), unconditioned stimulus reinforcers (US), and conditioned responses (CR). Are the learned properties of a sound differentially represented at various levels of the auditory pathway? Which are the brain structures related to attentional and learning processes involved in associative learning? Two experimental protocols have been designed to address these questions using a combination of classical and operant conditioning paradigms in conjunction with autoradiographic 2-DG techniques for the study of behavior in freely moving animals. The basic idea is to quantitate the uptake of 2-DG in the brain of rats during a variety of different behavioral conditioning and control situations. The proposed experiments manipulate the specific components involved in auditory conditioning (CS, US, CR) in an effort to discriminate the neural representation, in terms of 2-DG uptake, of these components independently or combined in paired and unpaired trials. In the first protocol two CSs will be compared, using a differential paradigm with reinforced (CS+) and nonreinforced (CS-) presentations, in order to discriminate the tonotopic from the reinforcing effects of CSs in terms of 2-DG uptake. The 2- DG method provides a tool that allows simultaneous visualization of tonotopic representation and functional activity in the auditory system. This method will be used also in a second protocol comparing the effects of identical CS-US pairings on the brains of four groups of rats: performing animals trained to bar press for reward during a sound signal (discriminative group), or bar pressing regardless of sound (nondiscriminative group), and rats yoked to the above groups and subjected to paired CS-US (classical group) and unpaired CS-US (control group), respectively. It is expected that comparisons using complementary stimulus- response conditions will serve to elucidate the neuroanatomical structures related to the specific components involved in auditory conditioning. The most important outcome of the proposed research would be the identification and functional mapping of rat brain structures responsible for the associative learning and memory of auditory stimuli.

This action is to support the international participants who are to attend a workshop dealing with metabolic mapping techniques for brain imaging during behavioral functions. This workshop will be the first meeting to review state-of-the-art applications of a new generation of cell metabolic mapping techniques capable of visually imaging brain functions related to animal learning and behavior. The potential impact of these functional mapping techniques for elucidating brain mechanisms of behavior is enormous. This workshop brings together leaders in this field from around the world and seeks to formulate recommendations for the directions of future research.

9222075 Gonzalez-Lima Brain metabolic mapping techniques have the potential of providing information about functional interactions within entire neural systems. Large quantities of data can be obtained from mapping studies, but an analytic technique to make sense of the complex network interactions that take place in the brain has not been available. Structural modeling may provide such a technique by combining the anatomical connectivity with the covariation in the activity between brain regions. Functional strengths of anatomical connections between the structures that form a neural system could be quantified by assigning numerical values to the links. Changes in these values could be used as indices of how information is processed and modified within the brain in a given situation. The purpose of this proposal is to use existing metabolic data from auditory learning experiments to develop structural models of auditory and nonauditory systems. The proposed methods will also be evaluated using simulated data with known relationships.***

A fundamental problem in the neurobiology of learning and memory is understanding the neural mechanisms of extinction. Behavior acquired as the result of Pavlovian conditioning can be extinguished by presenting the conditioned stimulus (CS) repeatedly without the unconditioned stimulus (US); this is known as the extinction effect. Although many neural activity studies of extinction imply that extinction is the reversal of acquisition, the behavioral phenomena of spontaneous recovery and disinhibition suggest that this is not the case and that extinction does not result in the loss or unlearning of the CS- US association in the brain. The behavioral training paradigm of Pavlovian conditioned suppression (conditioned emotional response, or CER procedure) will be used in all the proposed studies. The brain metabolic effects of extinction will be assessed with uptake of fluorodeoxyglucose (FDG). Metabolic responses from experimental rats will be compared to those of control rats exposed to the same tone to identify which regional activity changes occur in response to the tone conditioned stimulus (CS) after extinction of the CER. In addition, we will examine which of these brain metabolic activity changes are correlated with variations in the behavioral performance of each subject. The specific aims are to use the FDG brain mapping technique to test three hypotheses: 1) The hypothesis that extinction is the opposite of acquisition, which predicts that extinction involves the loss of unlearning of the CS-US associative effects on the brain; 2) The hypothesis that extinction is similar to long-term habituation, which suggests that CS salience of the tone will be modulated in auditory and arousal systems; and 3) Pavlov s hypothesis that extinction is a form of inhibition of the conditioned response. Specifically, it is predicted that the CER extinction effect is due to the inhibition of the neural representation of the CS-CER association in the prefrontal cortex and central amygdala. In contrast, reversals of learning effects on other neural circuits are expected to be minor during extinction due to the savings of CS-US associative effects unrelated to CER inhibition. In the CER paradigm, a better understanding of extinction mechanisms may also have important clinical implications, such as the therapeutic use of extinction to reduce undesired conditioned fears.

[unreadable] DESCRIPTION (provided by applicant): A fundamental problem in the physiology of learning and memory is to understand the neural mechanisms of extinction and other forms of behavioral inhibition. In addition, neuroimaging investigations of extinction effects in Pavlovian paradigms are of interest because Pavlovian conditioning is impaired with aging and in Alzheimer's disease. An extinction procedure after Pavlovian conditioning is a behavioral procedure in which the conditioned stimulus (CS) is repeatedly presented without the unconditioned stimulus (US). This extinction procedure results in a decline in conditioned behavior that is known as an extinction effect. In the conditioned emotional response (CER) paradigm, a better understanding of extinction mechanisms may also have important clinical implications for using extinction in therapeutic situations, such as reduction of undesired conditioned fears. Relief from fear is a major concern in public health. Although many neural studies of extinction imply that extinction is the reversal of acquisition, the behavioral phenomena of spontaneous recovery and disinhibition suggest that this is not the case and that extinction does not result in the loss or unlearning of the CS-US association in the brain. The specific aims are to test three hypotheses: 1) The hypothesis that extinction is the opposite of acquisition, which predicts that extinction involves the loss or unlearning of the CS-US associative effects on the brain; 2) The hypothesis that extinction is a form of contextual learning, which suggests that extinction depends on neural input from both the CS and the context; and 3) Pavlov's hypothesis that extinction is a form of inhibition of the conditioned response. The brain metabolic effects of extinction will be evaluated with uptake of fluorodeoxyglucose (FDG). Metabolic data from experimental rats will be compared to those of control rats exposed to the same tone to map regional brain activity changes occurring in response to the tone CS after extinction of the CER. Brain metabolic : activity (FDG data) will also be correlated with the behavioral performance of each subject during training and testing sessions (behavioral data). It is predicted that the CER extinction effect is mainly due to the inhibition of the neural representation of the CS-CER association in the prefrontal cortex. In contrast, reversals of learning effects on other neural circuits are expected to be minor during extinction due to the savings of CS-US associative effects unrelated to CER inhibition.

[unreadable] DESCRIPTION (provided by applicant): The Texas Consortium in Behavioral Neuroscience started in 2002 as the first regional training consortium in the USA with the mission to increase the number of first-rate behavioral neuroscientists from underrepresented populations. It offers a new model of inter-institutional cooperation, resource-sharing, networking and supportive climate conducive to a superior research education and professional development. It creates opportunities for the success of trainees with a gift of exceptional aptitude for science that have been historically underserved by traditional training programs. It is dedicated to opening doors to many meritorious individuals for whom doors have traditionally been closed. It seeks funding to support 10 predoctoral and 5 postdoctoral trainees from underrepresented ethnic and racial groups, individuals with disabilities, and individuals from disadvantaged backgrounds, who will conduct research relevant to NIMH, NIDA and NINDS. This innovative consortium enhances the cooperation and resource allocation among 5 institutions and unifies their training effort under the leadership of highly qualified neuroscientists with proven knowledge of successful training. The faculty comprises 26 NIH-funded PIs collaborating in research and training and committed to increasing diversity, selected from 5 Texas institutions with successful records of cooperation and training of underrepresented groups: University of Texas at Austin, University of Texas at San Antonio, University of Texas Health Science Center at San Antonio, Texas A&M University, and Texas A&M System Health Science Center. Broadly-based training spans behavioral, biomedical, and translational research, including neuroimaging, sychopharmacology, electrophysiology and neurobiology of behavioral functions and disorders. Training emphasizes professional development, grant writing and oral and written communication skills, as well as courses in brain and behavior, research ethics, experimental design and statistics. Trainee success is increased by a regional network with a critical mass of successful faculty and peers as role models, by professional enrichment activities, and by a responsive mentor-based learning climate. Strengths of this program include: 1) the large pool of qualified Hispanic students in the region, 2) the productivity and success of past and current trainees, 3) the professional enrichment and networking opportunities beyond those provided by the individual institutions, 4) the quality and relevant experience of the faculty and advisory committee, and 5) the inter- institutional opportunities for translational research. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Helplessness, a behavioral state of passivity with feelings of uncontrollability, is a common component of depression and post-traumatic stress disorder (PTSD). Even though stress plays a well-understood role in these disorders, there is a need to investigate congenital (inborn) neurobiological predispositions that underlie the helplessness trait, because only a minority of people develops depression or PTSD following stress or trauma. The broad objective of the proposed research is to better understand how congenital predisposition alters brain and behavior by studying the congenitally helpless rat - a selectively bred strain which shows the helplessness trait. The first aim is to further characterize this model behaviorally with separate tests in adult rats to ascertain whether congenitally helpless rats show a temperamental profile resembling individuals susceptible to PTSD: high exploration in novel environments, low reward sensitivity, and an exaggerated response to fear-evoking stimuli. The second aim is to metabolically map the brains of naive congenitally helpless rats at critical developmental stages in order to identify the underlying brain alterations. It is anticipated based on preliminary data that brains of newborn congenitally helpless rats will show innate reductions in interregional correlations of brain activity, particularly between forebrain and brainstem regions. This congenital alteration may subsequently impair feedback to the hypothalamic-pituitary-adrenal (HPA) axis. The third aim is to map the effects of the antidepressant fluoxetine on the brains of congenitally helpless rats. It is hypothesized that fluoxetine antidepressant effects may be mediated by decreasing metabolism in the lateral habenula. The habenula may provide a major modulatory influence on the HPA axis through its inputs to septohippocampal and monoaminergic systems. Brain metabolic effects will be evaluated with quantitative histochemistry of cytochrome oxidase because this method offers important advantages for mapping changes in neurobiological predispositions. Cytochrome oxidase is unique in that it marks cumulative, long-term neuronal activity, thus making it ideal for assessing baseline brain differences in animals from different genetic strains and in response to chronic antidepressant administration. Greater knowledge of brain mechanisms underlying the congenital predisposition to helplessness would be beneficial to develop more effective treatments for affective disorders.

Abstract This project will develop a novel infrared-based neuro-stimulation tool for specifically modulating neural circuitry. Transcranial infrared brain stimulation (TIBS) at 1064 nm will be developed as a new tool for non- invasive neuromodulation of the human brain. TIBS with low-power density (mW/cm2) and high-energy density (J/cm2) monochromatic laser is safe and can potentially modulate human brain function in a non-thermal manner. The mechanism of TIBS is based on the premise that infrared laser gives rise to photo-oxidation of cytochrome c oxidase (CCO), the respiratory enzyme in mitochondria that catalyzes the metabolic use of oxygen. The brain is critically dependent on oxygen metabolism for its physiological functions. Recently, our team has shown that TIBS delivered to the human prefrontal cortex results in significant increases of cerebral metabolism and oxygenation. These new and promising results have encouraged us to respond to the RFA, for developing TIBS as a novel non-invasive neuromodulation tool. Compared to existing electrical and magnetic tools for neuromodulation, TIBS (1) has no need to worry about excitatory versus inhibitory setup, (2) is easy to select stimulation site given the desired cortical region for stimulation, (3) has no need to design complicated probe montage, (4) can control spatial focality by varying the laser exposure aperture, (5) produces minimal discomfort on the participant?s head without any risk of seizures, (6) is low-cost, portable, and easy to move along with the participants, (7) has solid scientific premise and understanding of its working mechanism supported by many animal studies and recent human investigations. (8) While TIBS may be more effective to cortical regions because it uses infrared light with the limitation of penetration depth, our preliminary data show that TIBS does modulate deeper regions of the human brain and alter brain circuitry across the entire brain. The proposed project has two highly-focused, specific aims that will involve non-invasive controlled studies of healthy participants in three sites of the University of Texas. Aim 1 will determine the penetration depth, thermal effects, spatial resolution, and mechanism of TIBS delivered on the human forehead. The hypothesis for Aim 1 is that TIBS can reach the human cortex non-invasively and can significantly increase the oxidized state of CCO and promote cerebral oxygenation. Aim 2 will map and image large-scale, dynamic, electrophysiological and hemodynamic effects in neural circuitry that interact in both time and space during and after prefrontal TIBS. The hypothesis for Aim 2 is that prefrontal TIBS modulates electrophysiological and hemodynamic functions in a fronto-parieto-occipital network. We will accomplish these aims by an expert multidisciplinary team that will utilize advanced multi-modal optical imaging and electrophysiological methods with high spatiotemporal resolution, including diffusion optical tomography based on near-infrared spectroscopy techniques and EEG brain tomography. The success of this project will develop TIBS as a new non-invasive neuromodulation tool for future research and treatment of diverse brain disorders.