Lesions of the thalamic reticular nucleus or the basal forebrain impair Pavlovian eyeblink conditioning and attenuate learning-related multiple-unit activity in the mediodorsal nucleus of the thalamus
2
Citation
47
Reference
10
Related Paper
Abstract:
Rabbits received ibotenic acid lesions of the thalamic reticular nucleus or the basal forebrain, or sham lesions, and had multiple-unit recording electrodes implanted in the mediodorsal nucleus of the thalamus (MD). Animals were compared on four sessions of simple Pavlovian conditioning using a tone conditioned stimulus (CS) and periorbital electric shock unconditioned stimulus (US). Eyeblink (EB) and heart rate (HR) responses were recorded, as well as multiple-unit activity (MUA) from MD. MD MUA in sham-lesioned animals showed small but consistent increases in response to the CS. Lesions of either the basal forebrain or the thalamic reticular nucleus decreased the magnitude of the MUA changes recorded from MD and impaired acquisition of the EB conditioned response (CR). Reticular nucleus, but not basal forebrain, lesions slightly enhanced the magnitude of the HR CR. Since MD’s efferent projections are to the prefrontal cortex, these results support the idea that MD, possibly due to its forebrain-reticular afferent connections, may participate in a “response selection” function of the prefrontal cortex.Keywords:
Caudate nucleus
Reticular connective tissue
Forebrain
Reticular activating system
Neurochemical
Reticular activating system
Reticular connective tissue
Forebrain
Sleep
Neuroscience of sleep
Cite
Citations (40)
▪ Abstract Thalamocortical activity exhibits two distinct states: (a) synchronized rhythmic activity in the form of delta, spindle, and other slow waves during EEG-synchronized sleep and (b) tonic activity during waking and rapid-eye-movement sleep. Spindle waves are generated largely through a cyclical interaction between thalamocortical and thalamic reticular neurons involving both the intrinsic membrane properties of these cells and their anatomical interconnections. Specific alterations in the interactions between these cells can result in the generation of paroxysmal events resembling absence seizures in children. The release of several different neurotransmitters from the brain stem, hypothalamus, basal forebrain, and cerebral cortex results in a depolarization of thalamocortical and thalamic reticular neurons and an enhanced excitability in many cortical pyramidal cells, thereby suppressing the generation of sleep rhythms and promoting a state that is conducive to sensory processing and cognition.
Tonic (physiology)
Reticular activating system
Neuroscience of sleep
Sleep spindle
Reticular connective tissue
Forebrain
Thalamic reticular nucleus
Cite
Citations (1,247)
Thalamic reticular nucleus
Reticular activating system
Reticular connective tissue
Cite
Citations (198)
Abstract The reticular activating system consists mostly of ascending noradrenergic and cholinergic projections originating in the brainstem. These projections enter the cortex, thalamus and basal forebrain, and mediate increases in wakefulness and arousal. Contemporary hypotheses describe these systems as actively regulated afferent components of forebrain circuits mediating defined cognitive processes.
Reticular activating system
Forebrain
Reticular connective tissue
Cite
Citations (6)
Rabbits received ibotenic acid lesions of the thalamic reticular nucleus or the basal forebrain, or sham lesions, and had multiple-unit recording electrodes implanted in the mediodorsal nucleus of the thalamus (MD). Animals were compared on four sessions of simple Pavlovian conditioning using a tone conditioned stimulus (CS) and periorbital electric shock unconditioned stimulus (US). Eyeblink (EB) and heart rate (HR) responses were recorded, as well as multiple-unit activity (MUA) from MD. MD MUA in sham-lesioned animals showed small but consistent increases in response to the CS. Lesions of either the basal forebrain or the thalamic reticular nucleus decreased the magnitude of the MUA changes recorded from MD and impaired acquisition of the EB conditioned response (CR). Reticular nucleus, but not basal forebrain, lesions slightly enhanced the magnitude of the HR CR. Since MD’s efferent projections are to the prefrontal cortex, these results support the idea that MD, possibly due to its forebrain-reticular afferent connections, may participate in a “response selection” function of the prefrontal cortex.
Caudate nucleus
Reticular connective tissue
Forebrain
Reticular activating system
Cite
Citations (2)
Persistent vegetative state
Reticular activating system
Coma (optics)
Forebrain
Cite
Citations (11)
Neocortex network activity varies from a desynchronized or activated state typical of arousal to a synchronized or deactivated state typical of quiescence. Such changes are usually attributed to the effects of neuromodulators released in the neocortex by nonspecific activating systems originating in basal forebrain and brain stem reticular formation. As a result, the only role attributed to thalamocortical cells projecting to primary sensory areas, such as barrel cortex, is to transmit sensory information. However, thalamocortical cells can undergo significant changes in spontaneous tonic firing as a function of state, although the role of such variations is unknown. Here we show that the tonic firing level of thalamocortical cells, produced by cholinergic and noradrenergic stimulation of the somatosensory thalamus in urethane-anesthetized rats, controls neocortex activation and deactivation. Thus in addition to its well-known role in the relay of sensory information, the thalamus can control the state of neocortex activation, which may complement the established roles in this regard of basal forebrain and brain stem nuclei. Because of the topographical organization of primary thalamocortical pathways, this mechanism provides a means by which area-specific neocortical activation can occur, which may be useful for modality-specific sensory processing or selective attention.
Neocortex
Tonic (physiology)
Forebrain
Reticular activating system
Reticular connective tissue
Thalamic reticular nucleus
Cite
Citations (110)
Forebrain
Thalamic reticular nucleus
Reticular activating system
Reticular connective tissue
Cite
Citations (575)
The "ascending reticular activating system" theory proposed that neurons in the upper brainstem reticular formation projected to forebrain targets that promoted wakefulness. More recent formulations have emphasized that most neurons at the pontomesencephalic junction that participate in these pathways are actually in monoaminergic and cholinergic cell groups. However, cell-specific lesions of these cell groups have never been able to reproduce the deep coma seen after acute paramedian midbrain lesions that transect ascending axons at the caudal midbrain level. To determine whether the cortical afferents from the thalamus or the basal forebrain were more important in maintaining arousal, we first placed large cell-body-specific lesions in these targets. Surprisingly, extensive thalamic lesions had little effect on electroencephalographic (EEG) or behavioral measures of wakefulness or on c-Fos expression by cortical neurons during wakefulness. In contrast, animals with large basal forebrain lesions were behaviorally unresponsive and had a monotonous sub-1-Hz EEG, and little cortical c-Fos expression during continuous gentle handling. We then retrogradely labeled inputs to the basal forebrain from the upper brainstem, and found a substantial input from glutamatergic neurons in the parabrachial nucleus and adjacent precoeruleus area. Cell-specific lesions of the parabrachial-precoeruleus complex produced behavioral unresponsiveness, a monotonous sub-1-Hz cortical EEG, and loss of cortical c-Fos expression during gentle handling. These experiments indicate that in rats the reticulo-thalamo-cortical pathway may play a very limited role in behavioral or electrocortical arousal, whereas the projection from the parabrachial nucleus and precoeruleus region, relayed by the basal forebrain to the cerebral cortex, may be critical for this process.
Forebrain
Reticular activating system
Cite
Citations (464)
Forebrain
Midbrain reticular formation
Reticular connective tissue
Reticular activating system
Cite
Citations (2)