The locus coeruleus (LC) is the brainstem neuromodulatory nucleus responsible for most of the norepinephrine (NE) released in the brain. It has widespread projections throughout the neocortex, and has a critical role in regulating arousal and wakefulness. In addition, the LC-NE neuromodulatory system is currently thought to play a role in several cognitive functions such as attention, emotion, decision making and learning and memory.
Example from Astafiev et al., 2010, Science: neuromelanin image (N = 10):
Region of Interest image (ROI):
ROI Nifti image: LC nifti
The LC is difficult to identify on conventional MR images due to its small size (~ 1 cm in length in humans) and its location deep down in the brainstem, immediately adjacent to the fourth ventricle. On neuromelanin-sensitive images, it is identified as a spotty high signal intensity area in the upper pontine tegmentum. This is because the noradrenergic neurons in the LC contain abundant neuromelanin (like the neurons in the SNc).
locus coeruleus [all] and fmri [all] locus coeruleus [all] and projections [all]
=Reviews on anatomy, physiology and function of the locus coeruleus-norepinephrine system:=
=Classic paper about the effects of NE (and DA) on target neurons:=
=Other subcortical inputs:=
The LC innervates almost the entire forebrain, with the exception of the striatum. The LC has widespread projections throughout the neocortex, thalamus, midbrain, cerebellum and spinal cord (Aston-Jones, Foote, & Bloom, 1984; Berridge & Waterhouse, 2003).
=Comparative anatomy of the distribution of noradrenergic and dopaminergic projections in the rat brain= (From: Sara, 2009, Nat Rev Neurosci)
ACC, anterior cingulate cortex; AON, anterior olfactory nucleus; AP-VAB, ansa peduncularis–ventral amygdaloid bundle system; BS, brainstem nuclei; C, cingulum; CC, corpus callosum; CER, cerebellum; CTT, central tegmental tract; CTX, cortex; DB, dorsal bundle; DPS, dorsal periventricular system; F, fornix; FC, frontal cortex; FR, fasiculus retroflexus; H, hypothalamus; HF, hippocampal formation; ML, medial lemiscus; MT, mamillothalamic tract; OB, olfactory bulb; OT, olfactory tract; pc, pars compacta; PC, piriform cortex; PRC, perirhinal cortex; PT, pretectal area; RF, reticular formation; S, septum; SC, spinal cord; ST, stria terminalis; T, tectum; TH, thalamus)
The LC is responsible for most of the norepinephrine (NE) released in the brain. Effects of NE on target neurons depends on the receptor that is activated (Foote et al., 1983; reviewed in Berridge and Waterhouse, 2003): alpha1 adrenoceptor activation is often associated with excitation, and alpha2 adrenoceptor activation (the dominant type within LC itself) is associated with inhibition (Rogawski and Aghajanian, 1982; Williams et al., 1985). In addition, NE augments evoked responses (either excitatory or inhibitory), while decreasing spontaneous activity in many target neurons (Waterhouse et al., 1980, 1984; Waterhouse and Woodward, 1980). Thus, modulation of neuronal responses to other inputs is a prominent effect of NE on target neurons. This modulatory action of NE was captured in an early computational model as an increase in the gain of the activation function of neural network units (Servan-Schreiber, Printz, & Cohen, 1990).
For a long time, the LC-NE system has been associated with basic functions as arousal and environmental responsiveness. Tonic activity of LC-NE neurons strongly covaries with stages of the sleep-waking cycle: they fire most rapidly during waking, slowly during drowsiness and slow-wave/non-REM sleep, and become virtually silent during REM sleep (Hobson et al., 1975; Aston-Jones and Bloom, 1981a; Rasmussen et al., 1986; Rajkowski et al., 1998). In addition, LC neurons in rats and monkeys activate robustly following salient stimuli in many modalities that elicit behavioral responses (Foote et al., 1980; Aston-Jones and Bloom, 1981b; Grant et al., 1988).
Recent research has shown that the LC-NE system has specific functions in the control of behavior (e.g., Aston-Jones & Cohen, 2005; Sara, 2009). According to a recent theory, the adaptive gain theory (Aston-Jones & Cohen, 2005), the LC-NE system has a critical role in the optimization of behavioral performance — by facilitating responses to motivationally significant stimuli and regulating the tradeoff between exploitative and exploratory behaviors.
link to Aston-Jones & Cohen, 2005, Annu Rev Neurosci
Opioids inhibit the firing of LC neurons, and opiate withdrawal induces hyperactivity of LC neurons.
Coordinates (x, y, z): [-4, -37, -25] , [6, -38, -26] average from Keren et al (2009) and Astafiev et al (2010)
Specific study coordinates (if not too many)
|Keren 2009||neuromelanin signal||-3.7||-37||-24|
|Keren 2009||neuromelanin signal||-4.7||-37||-27|
|Keren 2009||neuromelanin signal||5.8||-37||-27|
|Astafiev 2010||neuromelanin signal||-3.2||-38||-25|
|Astafiev 2010||neuromelanin signal||5.4||-38||-25|