Dysfunction of cholinergic and dopaminergic systems has been implicated in memory function de cits that are core pathology and associated features of several neurological disorders. However, in order to develop more effective treatments, it is crucial to better understand how different aspects of learning and memory are modulated by these neuromodulatory systems. Using optogenetic stimulation or silencing, this thesis aims to investigate the effects of cholinergic and dopaminergic modulation on various hippocamal learning and memory processes. To understand how these neuromodulatory systems modulate hippocampal network activity, I first examined their effects on hippocampal local field potentials in urethane-anaesthetised mice. I demonstrated that optogenetic cholinergic activation suppressed slow oscillations, shifting brain activity to a state dominated by theta and gamma oscillations. In contrast, dopaminergic activation suppressed gamma oscillations. Second, to directly probe the effects of neuromodulation on different stages of spatial learning, I acutely activated or inactivated cholinergic or dopaminergic neurons during various behavioural tasks. My findings suggested that cholinergic activation, solely during the reward phase of a long-term spatial memory task, slowed place learning, highlighting the importance of temporally-precise neuromodulation. Moreover, dopaminergic stimulation may enhance place learning of a food rewarded task, supporting a role for dopamine in spatial learning. In addition, I tested the effects of cholinergic and dopaminergic modulation on reversal learning and found that cholinergic inactivation and dopaminergic activation appear to impair this process. Together, these findings emphasise the importance of cholinergic and dopaminergic modulation in learning and memory. They suggest that precise timing of neuromodulator action is critical for optimal learning and memory performance, and that acetylcholine and dopamine support complementary processes that allow for effective learning and adaptation to changing environments.

Cell modulation poses an invaluable role in understanding the biophysics, deciphering the neural circuits, and exploring clinical treatment of diseases. Optoacoustic cell modulation is an emerging modality benefiting from the merits of ultrasound with high penetration depth as well as photons with high spatial precision. My thesis work focused on the development of a fiber optoacoustic emitter for neural stimulation and the study of biomolecular mechanisms underlying optoacoustic cell modulation. To enable region specific and high-efficiency cell modulation, we developed a fiber-based optoacoustic emitter (FOE), serving as a miniaturized ultrasound point source, with sub-millimeter confinement. By modifying acoustic damping and light absorption performance, controllable frequencies in the range of 0.083 MHz to 5.500 MHz are achieved and further induce cell membrane sonoporation with frequency dependent efficiency. These data demonstrate the potential of FOE in region-specific drug delivery, gene transfection and neurostimulation. To achieve neuromodulation at single cell spatial resolution, we further developed a tapered fiber optoacoustic emitter (TFOE) enabling stimulation of single neurons and subcellular structures. The highly confined ultrasound enabled integration of the optoacoustic stimulation with stable patch clamp recording on single neurons for the first time. Cell-type-specific response of excitatory and inhibitory neurons to acoustic stimulation was unveiled. Towards understanding the biomolecular mechanisms of optoacoustic cell modulation, we show that optoacoustic excites primary cortical neurons through specific calcium-selective mechanosensitive ion channels with the assistant of calcium amplifier channel and voltage-gated channels. Pharmacological inhibition of specific ion channels leads to reduced responses, while over-expressing these channels results in stronger stimulation. These results shed new insights into the mechanism of ultrasound neurostimulation. Together, these findings offer a platform for understanding the mechanism of acoustic cell modulation as well as non-genetic, high precision cell modulation method enabling treatment of diseases. / 2025-09-21T00:00:00Z

Although parasympathetic activity (PNS) is the primary driver and sympathetic activity (SNS) is a significant inhibitor of colonic propulsive activity, they are rarely measured, and hence, they almost play no role in diagnosing dysfunction or standard treatments for chronic conditions such as refractory constipation. We aimed to develop methodologies for the assessment of autonomic nervous system (ANS) activity, establish criteria for autonomic dysfunction, and study if stimulation of lumbar and sacral autonomic nerves using low-level laser therapy (LLLT) could affect the ANS and explore it as a potential treatment of autonomic dysfunction to restore colonic motility. By studying the active standing test and the table tilt test as a method to evoke activity in the ANS, we rejected LF power, SD1 and SD2 of Poincare plot, Pre-ejection-period (PEP), complex-correlation-measure (CCM) and detrended fluctuation analysis (DFA). Respiratory-Sinus-Arrhythmia (RSA), Root-Mean-Square-of-Successive-Differences (RMSSD) were selected for PNS activity, the Baevsky’s-Stress-Index (SI) was chosen for SNS activity, and SI/RSA and SI/RMSSD were introduced as a measure of autonomic balance. We explored high-resolution-colonic-manometry with concurrent electrocardiography to observe whether these parameters could be associated with ANS changes during colonic motor patterns. High-amplitude-propagating-pressure-waves were associated with a strong parasympathetic activity and decreased sympathetic activity. Comparing ANS reactivity of patients with severe motility disorders to controls in response to postural changes, we observed that most patients have low PNS and elevated SNS baseline activity and reactivity. This established a way to evaluate autonomic dysfunction in patients with colon motor disorders. A single session of LLLT using LED and laser light on the lumbar and sacral spine in 41 patients with chronic gastrointestinal motor dysfunction indicated that treatments with LED light followed by laser light significantly increased parasympathetic activity and decreased sympathetic nervous system activities. These results initiated a study into the effects of LLLT on restoring autonomic dysfunction in chronic refractory colonic motility disorders. / Thesis / Doctor of Philosophy (PhD)

We investigated the origins, neural modulation, ionic mechanisms, and electrical coupling properties of the pacemaker systems in the canine ileum by simultaneously recording the intracellular electrical activity and accompanying mechanical activity in cross-sectioned slabs of the muscularis extema or in the isolated circular muscle. In the whole thickness preparation, intracellular recordings were taken from the circular muscle near the myenteric plexus (MyP), deep muscular plexus (DMP), and intermediate areas between the MyP and DMP and in the isolated circular muscle preparation from similar areas except near the myenteric plexus. One type of slow wave, sigmoidal or triangular in shape, was recorded from impalements near the DMP region in the whole-thickness preparation. Another type observed from the MyP region oscillated at nearly the same frequency (9-10 cycles/min) and was characterized by a fast upstroke and a square shape. A mixture of these two patterns was recorded in intermediate areas (the outer circular muscle or OCM) while triangular slow waves were present near the the submucosal plexus (SMP) inner circular muscle. Neither type of slow waves was affected by atropine, guanethidine, propranolol, and phentolamine (all 1 μM). Under these conditions of inhibition of NANC (non-adrenergic, non-cholinergic) nerves, electrical field stimulation (EFS) produced a fast, monophasic inhibitory junction potential (IJP) followed by a triggered slow wave (TSW) which could be premature or delayed and whose amplitude was maximum near the MyP region and decayed progressively in the other areas (minimum in SMP region). The K+ channel blocker, apamin at 10⁻⁶ M, did not affect resting membrane potentials or spontaneous slow waves but inhibited the amplitude of the IJP up to 70% and slightly but significantly enhanced (30%) the amplitude of the TSW. Long duration, single pulses (50-100 msec square waves, 10-20 V) elicited TSWs without IJPs. Both the slow waves and TSWs were associated with contractions of circular muscle which were significantly enhanced by apamin but not by blockers of adrenergic and cholinergic nerves. When the IJPs recorded near the MyP or DMP were abolished by tetrodotoxin (TTX, 1 μM) or by the NO synthase (NOS) inhibitor, N^ω nitro L-arginine (L-NNA, 50 μM), the occurrence of the TSW in response to EFS was advanced in time and increased in amplitude. The effects of L-NNA were reversed by L-but not D-arginine (both 1 mM). L-arginine significantly prolonged the durations of IJPs from the MyP and DMP regions. In contrast, the N-type Ca²⁺ channel blocker ω-conotoxin GVIA (ω-CTX, 1-3 x10⁻⁷M) abolished the IJP but delayed the induction of the TSW. Subsequent addition of either TTX or L-NNA advanced the onset of the TSW. The TSWs elicited by 50-100 msec single pulses were resistant to TTX, ω-CTX, or L-NNA. All treatments which abolished the IJP significantly increased contractions of circular muscle associated with spontaneous slow waves and TSWs. In the isolated circular muscle preparation (with the DMP intact) triangular slow waves were recorded near the DMP or close to the MyP border. The frequency and amplitude of the slow waves recorded near the DMP were significantly smaller than those recorded in similar areas in the full thickness preparation. EFS of this preparation evoked IJPs of 18-20 mV in amplitude. The IJPs were biphasic, lasted 5s and showed a fast and a slow component. No TSW occurred after the fast component of the IJPs; slow repolarization was observed instead. Long duration single pulses did not induce TSWs. In this preparation, the NOS inhibitor, N^ω nitro L-arginine methyl ester (L-NAME, 3x10⁻⁴ M), abolished the IJPs and regularized the slow waves, but TSWs could not be evoked. Superfusion of inhibitory neuromediators had different effects on pacemaking activity. SIN-1, a donor of NO, hyperpolarized the membrane, significantly increased slow wave frequency but reduced its amplitude, and abolished contractions. VIP (less effective) and PACAP (more effective) reduced slow wave frequency and amplitude without changing resting membrane potentials. P ACAP, but not VIP, increased circular muscle tone at 10⁻⁶ M. Nifedipine (10⁻⁷ and 3 X 10⁻⁷ M), an L-type calcium channel blocker, did not modify the shape of slow waves in any area of the full thickness preparation. It also did not reduce the amplitude of the IJP or TSW. Ni²⁺ at 200 μM, a Ca²⁺ channel blocker, inhibited slow wave frequency and amplitude and contractions. In Ca²⁺ -free Krebs (0.1 mM EGTA) for 10-15 min, the amplitude and frequency of the slow waves were gradually reduced. The TSW in response to 100 msec single pulses was still recorded near the MyP but never near the DMP region. The inhibitory effect of Ca²⁺ -free solution on slow wave amplitude was more rapid in onset near the DMP region. The intracellular Ca²⁺ store pump inhibitor, cyclopiazonic acid (10-30 μM), enhanced slow wave frequency and contractions. This differential sensitivity to removal of Ca²⁺ may be related to the morphological and functional observations which suggested that different electrical coupling properties between the pacemaker networks existed. The MyP pacemakers were less electrically well-coupled by visible gap junctions (low resistive cell-to-cell contacts) to outer circular muscle and hence showed greater susceptibility to 1 mM octanol (a gap junction blocker). The DMP pacemakers made numerous gap junction contacts to circular muscle, and slow waves paced from this region were less susceptible to 1 mM octanol. We conclude that 1) the pacemaker system of the canine ileum consists of two types of pacemakers that correspond to the presence of two networks of pacemaker cells found in the MyP and the DMP. The MyP network appeared to dominate pacemaking activity. 2) The slow waves and the TSW originated independently of neural activity but were delayed by IJPs. The MyP and the DMP provide two independent inhibitory neural inputs, where NO is released to mediate IJPs and relaxation and influence the delay in the occurrence of the TSW. 3) The TSW originates exclusively from the MyP region from which it spreads passively to other areas. It can reset the timing of slow waves in both pacemaker networks. 4) Ca²⁺ entry through non L-or N-type Ca²⁺ channels initiates slow waves. Intracellular Ca²⁺ stores modulate slow waves. 5) Different nature of electrical coupling of the MyP and DMP pacemakers to circular muscle may explain the differential sensitivity of slow waves to Ca²⁺ removal and gap junction blockade. / Thesis / Master of Engineering (ME)

Background and Aims Sacral nerve stimulation (SNS) is an established therapy for faecal incontinence (FI). Percutaneous tibial nerve stimulation (PTNS) is a newer, less-invasive treatment. The effectiveness, cost and acceptability of these treatments have not been systematically compared. Methods A systematic review of neuromodulation interventions for FI and an investigator-blinded, randomised pilot trial of PTNS vs. SNS including parallel quantitative (clinical outcomes and cost) and qualitative studies. Results The systematic review determined on intention-to-treat, the median success rates for SNS were 63% (range 33-66%), 58% (range 52-81%) and 54% (range 50-58%) in the short, medium and long terms respectively. The success rate for PTNS was 59% at 12 months. In the pilot trial: 40 patients (39 female; mean age 59 years) met eligibility criteria. As designed, 23 were randomised to receive SNS and 17 PTNS. 15 patients progressed to permanent SNS implantation and 16 patients received a full course of PTNS. Within group effect sizes were marginally greater for SNS than PTNS on available case analysis. FI episodes per week at baseline, 3 months and 6 months follow-up: SNS median 5.75 (IQR 5.75-15.5 ) [mean 11.4 (SD 12.0)], 2.5 (2-4.5) [4.0 (4.0)], 1.75 (1.5-5) [4.9 (6.9)], vs. PTNS median 6.5 (IQR 2.5- 16.5) [mean 10.6 (SD 11.2)], 3.5 (0.75-7.25) [5.8 (6.9)], 2.5 (0.75-10.75) [6.3 (6.9)]. At least 50% improvement in FI episodes per week at 6 months: SNS 61% vs. PTNS 47%. Effect estimates for SNS with chronic implanted stimulation were larger (67% at 6 months). Clinical FI scores and quality of life improvements complemented these results. Qualitative analysis demonstrated a very high acceptability and safety profile for both treatments. Total costs were £2,906 (SD £122) per patient for PTNS and £12,748 (SD £4,175) for SNS. Conclusions Definitive trial data between SNS or PTNS is lacking. This RCT pilot study determined that in the short-term, SNS confers a small clinical benefit over PTNS for FI but is much more expensive.

A interação entre agentes inteligentes na disputa por recursos necessários à sobrevivência é um fato onipresente na luta pela vida. Este tipo de interação é estudado e formalizado matematicamente pela teoria dos jogos. Na literatura experimental encontramos vários estudos envolvendo primatas humanos e não humanos em tarefas de jogos estratégicos, mas, até o momento, não foi desenvolvido nenhum modelo deste comportamento com roedores. Estudos do comportamento animal mostram que estes aprendem e aprimoram este tipo de estratégias através de aprendizagem por reforço. O elemento central dos modelos computacionais de aprendizado por reforço é o sinal de violação de expectativa, que sinaliza o quanto um resultado difere, para mais ou para menos, do esperado. Este sinal é utilizado pelo agente para atualização dos valores e, assim, da probabilidade de escolha das opções. A pesquisa neurofisiológica tem consistentemente demonstrado que o sinal fásico emitido pelo sistema dopaminérgico conforma-se muito de perto às características do sinal descrito pela teoria computacional. Dessa maneira, os objetivos do presente estudo são pesquisar (1) se roedores são capazes de jogar um jogo estratégico simples e se a evolução do seu desempenho é consistente com o aprendizado por reforço e (2) se os efeitos de agonistas e antagonistas dopaminérgicos na estratégia de jogo são consistentes com a teoria segundo a qual o sinal dopaminérgico fásico desempenha função central na atualização constante da estratégia de jogo. Nossos resultados demonstram que, neste jogo estratégico, roedores efetivamente são capazes de um desempenho muito próximo do normativo, que seu desempenho é consistente com o aprendizado por reforço e, finalmente, que o sistema dopaminérgico está envolvido no processo de atualização da estratégia. / Intelligent agents competing for the resources necessary for survival is a universal factor in the struggle for life. This type of interaction has been studied and mathematically formalized by game theory. In scientific literature we have come across several studies involving human and non-human primates carrying out strategic game tasks; however, until now, no model for such behavior has been developed for rodents. Animal behavior studies have shown that animals learn and develop strategies through reinforcement learning. A central element of computational models of reinforcement learning is the reward-prediction error signal, which indicates how much a result differs, either positively or negatively, from the expected result. This signal is used by the agent to update the values of its options, and so their probability of being chosen. Neurophysiologic research has consistently shown that the phasic signal emitted by the dopamine system conforms very closely to the characteristics of the signal described by computational theory. The purposes of this study are: (1) to discover whether rodents are capable of playing a simple strategic game and whether the evolution of their performance is consistent with reinforcement learning; and (2) whether the effects of dopamine agonists and antagonists on game strategy are consistent with the theory that phasic dopamine signals have a primary role in the constant update of game strategy. Our results prove that, in this strategic game, rodents are effectively capable of finding a strategy that is very close to the normative one, that their performance is consistent with reinforcement learning and, finally, that the dopamine system is involved in the process of strategic updating.

Deep Brain Stimulation (DBS) is a developing therapeutic technique with a high potential to control and treat central nervous system diseases through neuromodulation. DBS utilizes through implanted electrodes that are inserted in the targeted brain structure. Being an emerging technology; neuromodulation introduces many challenges that are not yet comprehensively identified, characterized and resolved. The advancement of this technique requires qualitative and quantitative perception of the brain response to electrical stimulation which is controlled by the electric field distribution within the brain tissue. This can be realized by formulating the tissue-field interaction such that we will have a better understanding of the spatial extent and the direct effects of deep brain stimulation (DBS) on neurons activity. The focus of this research is to develop a model for encoding and decoding the neuron activity in the DBS region and to address all the parameters that affect this activity in order to have a complete understanding of the DBS problem and to develop a brain model that can be readily used in DBS analysis. Our goal is to study the immediate direct effects of the stimulating field and examine where the beneficial effects of DBS originate since the mechanism of DBS is not yet fully understand and hence an inclusive comprehensive performance study will be done for the DBS problem.

Despite having similar brains, related species can display divergent behaviors. Investigating the neural basis of such behavioral divergence can elucidate the neural mechanisms that allow behavioral change and identify neural mechanisms that influence the evolution of behavior. Fewer than three percent of Nudipleura (Mollusca, Opisthobranchia, Gastropoda) species have been documented to swim. However, Tritonia diomedea and Pleurobranchaea californica express analogous, independently evolved swim behaviors consisting of rhythmic, alternating dorsal and ventral flexions. The Tritonia and Pleurobranchaea swims are produced by central pattern generator (CPG) circuits containing homologous neurons named DSI and C2. Homologues of DSI have been identified throughout the Nudipleura, including in species that do not express a dorsal-ventral swim. It is unclear what neural mechanisms allow Tritonia and Pleurobranchaea to produce a rhythmic swim behavior using homologous neurons that are not rhythmic in the majority of Nudipleura species. Here, C2 homologues were also identified in species that do not express a dorsal-ventral swim. We found that certain electrophysiological properties of the DSI and C2 homologues were similar regardless of swim behavior. However, some synaptic connections differed in the non-dorsal-ventral swimming Hermissenda crassicornis compared to Tritonia and Pleurobranchaea. This suggests that particular CPG synaptic connections may play a role in dorsal-ventral swim expression. DSI modulates the strength of C2 synapses in Tritonia, and this serotonergic modulation appears to be necessary for Tritonia to swim. DSI modulation of C2 synapses was also found to be present in Pleurobranchaea. Moreover, serotonergic modulation was necessary for swimming in Pleurobranchaea. The extent of this neuromodulation also correlated with the swimming ability in individual Pleurobranchaea; as the modulatory effect increased, so too did the number of swim cycles produced. Conversely, DSI did not modulate the amplitude of C2 synapses in Hermissenda. This indicates that species differences in neuromodulation may account for the ability to produce a dorsal-ventral swim. The results indicate that differences in synaptic connections and neuromodulatory dynamics allow the expression of rhythmic swim behavior from homologous non-rhythmic components. Additionally, the results suggest that constraints on the nervous system may influence the neural mechanisms and behaviors that can evolve from homologous neural components.

During centrally orchestrated movements, the nervous system must distinguish between appropriate and inappropriate reflexes. I studied local postural flexion reflexes of the crayfish that are evoked by unexpected touch. An isolated abdomen was used which permitted recording and stimulating of tailfan afferents, nerve cord interneurons, and postural motor neurons. Stimulation of the afferents evoked a postural flexion response of the medium tonic and large phasic motor neurons of the superficial flexor nerve; a flexion motor program was then excited by stimulating descending interneurons. Afferent stimulation evoked a smaller motor response during the motor program than before or after. These results indicate that the postural reflex responses to sensory stimulation are inhibited at a site presynaptic to the motor neurons during the flexion motor program. Application of Picrotoxin (blocked inhibition) to the primary afferent-to-mechanosensory interneuron synapse did not prevent the modulation of the postural flexion reflex during the flexion motor program.

Deep Brain Stimulation (DBS) is a developing therapeutic technique with a high potential to control and treat central nervous system diseases through neuromodulation. DBS utilizes through implanted electrodes that are inserted in the targeted brain structure. Being an emerging technology; neuromodulation introduces many challenges that are not yet comprehensively identified, characterized and resolved. The advancement of this technique requires qualitative and quantitative perception of the brain response to electrical stimulation which is controlled by the electric field distribution within the brain tissue. This can be realized by formulating the tissue-field interaction such that we will have a better understanding of the spatial extent and the direct effects of deep brain stimulation (DBS) on neurons activity. The focus of this research is to develop a model for encoding and decoding the neuron activity in the DBS region and to address all the parameters that affect this activity in order to have a complete understanding of the DBS problem and to develop a brain model that can be readily used in DBS analysis. Our goal is to study the immediate direct effects of the stimulating field and examine where the beneficial effects of DBS originate since the mechanism of DBS is not yet fully understand and hence an inclusive comprehensive performance study will be done for the DBS problem.