Many neurons in the cat and monkey deep SC are uni-sensory.⇒
Visual receptive field sizes change in the deep SC with eccentricity, they do not in the superficial hamster SC.⇒
Anastasio and Patton model the deep SC using SOM learning.⇒
Anastasio and Patton present a model of multi-sensory integration in the superior colliculus which takes into account modulation by uni-sensory projections from cortical areas.⇒
In the model due to Anastasio and Patton, deep SC neurons combine cortical input multiplicatively with primary input.⇒
Anastasio and Patton's model is trained in two steps:
First, connections from primary input to deep SC neurons are adapted in a SOM-like fashion.
Then, connections from uni-sensory, parietal inputs are trained, following an anti-Hebbian regime.
The latter phase ensures the principles of modality-matching and cross-modality.⇒
Deactivating or stimulating certain parts of the the deeper layers of the SC induces arousal, freezing and escape behavior as well as a raise in blood pressure, heart rate, and respiration.
Reactions can be as complex as running and jumping.⇒
The motor map of in the dSC is retinotopic.⇒
The receptive fields of multisensory neurons in the deep SC which are close to one another are highly correlated.⇒
Wickelgren found the receptive fields of audio-visual neurons in the deep SC to have no sharp boundaries.⇒
Both visual and auditory neurons in the deep SC usually prefer moving stimuli and are direction selective.
The range of directions deep SC neurons are selective for is usally wide.⇒
Anastasio drop the strong probabilistic interpretation of SC neurons' firing patterns in their learning model.⇒
Some authors distinguish only superficial and deep superior colliculus.⇒
Certain neurons in the deep SC emit bursts of activity before making a saccade.⇒
The size and direction of a saccade before which deep SC neurons show the greatest activity depends on where they are in the SC: Neurons in medial regions of the SC tend to prefer saccades going up, neurons in lateral regions of the SC tend to prefer saccades going down.
Long saccades are preceded by strong activity of rostral neurons, short saccades by activity of caudal neurons.⇒
Deep SC neurons which have preferred saccades have these preferred saccades also in total darkness. They thus do not simply respond to the specific location of a visual stimulus.⇒
Robinson reports two types of motor neurons in the deep SC: One type has strong activity just (~20 milliseconds) before the onset of a saccade. The other type has gradually increasing activity whose peak is, again, around 12-20 milliseconds before onset.⇒
Currently, three types of saccade-related neurons are distinguished in the deep SC:
Microstimulation of OT neurons in the barn owl can evoke pupil dilation.⇒
Ablation of the superficial SC does not result in blindness or orienting deficiencies. Only when the deep SC is ablated do these deficiencies occur—a remarkable finding considering that the superficial SC is the main target of retinotectal projections.⇒
Superficial layers of the SC project to deep layers.⇒
Both deep and superficial layers in left and right SC project to the corresponding layer in the contralateral SC.⇒
There are excitatory and inhibitory connections from the deep to the superficial SC.⇒
The excitatory and inhibitory connections from the deep to the superficial SC and the connection from the superficial SC to LGN may be one route through which deep SC activity may reach cortex.⇒
There are inhibitory connections from deep SC to superficial SC (SGI to SGS).⇒
The ventral lateral geniculate nucleus projects to the deep SC.⇒
Some neurons in the dSC respond to an auditory stimulus with a single spike at its onset, some with sustained activity over the duration of the stimulus.⇒
Middlebrooks and Knudsen report on sharply delineated auditory receptive fields in some neurons in the deep cat SC, in which there is an optimal region from which stimuli elicit a stronger response than in other places in the RF.
A minority of deep SC neurons are omnidirectional, responding to sounds anywhere, albeit with a defined best area.⇒
There is considerable variability in the sharpness of spatial tuning in the responses to auditory stimuli of deep SC neurons.⇒
The visual and auditory maps in the deep SC are in spatial register.⇒
Auditory receptive fields tend to be greater and contain visual receptive fields in the deep SC of the owl.⇒
Neurons in the deep SC which show an enhancement in response to multisensory stimuli peak earlier.
The response profiles have superadditive, additive, and subadditive phases: Even for cross-sensory stimuli whose unisensory components are strong enough to elicit only an additive enhancement of the cumulated response, the response is superadditive over parts of the time course.⇒
The map of visual space in the superficial SC of the mouse is in rough topographic register with the map formed by the tactile receptive fields of whiskers (and other body hairs) in deeper layers.⇒
The receptive fields of certain neurons in the cat's deep SC shift when the eye position is changed. Thus, the map of auditory space in the deep SC is temporarily realigned to stay in register with the retinotopic map.⇒
SC receives input and represents all sensory modalities used in phasic orienting: vision, audition, somesthesis (haptic), nociceptic, infrared, electoceptive, magnetic, and ecolocation.⇒
The stratum griseum intermediale is the outermost lamina of the deep SC.⇒
The stratum album intermediale is the second-outermost lamina of the deep SC, below the stratum griseum intermediale.⇒
The stratum griseum profundum is the third-outmost lamina of the deep SC, below the stratum album intermediale.⇒
The stratum album profundum is the lowest lamina of the deep SC, below the stratum griseum profundum.⇒
The stratum album profundum borders to the periaqueductal gray.⇒
There are alternative nomenclatures for the layers of the deep sc.⇒
Deep SC neurons do react to stimuli based on color contrast. ⇒
There is reason to believe that color information reaches the SC via cortical routes.⇒
The mammalian SC is divided into seven layers with alternating fibrous and cellular layers.
The superficial layers include layers I-III, while the deep layers are layers IV-VII.
Some authors distinguish a third, intermediate, set of layers (IV,V).⇒
The deeper levels of SC are the targets of projections from cortex, auditory, somatosensory and motor systems in the brain.⇒
The deeper layers of the SC project strongly to brainstem, spinal cord, especially to those regions involved in moving eyes, ears, head and limbs, and to sensory and motor areas of thalamus.⇒
Visual receptive fields in the deeper SC are larger than in the superficial SC.⇒
The parts of the sensory map in the deeper SC corresponding to peripheral visual space have better representation than in the visual superficial SC.⇒
Do the parts of the sensory map in the deeper SC corresponding to peripheral visual space have better representation than in the visual superficial SC because they integrate more information; does auditory or tactile localization play a more important part in multisensory localization there?⇒
Neurons in the deep SC whose activity spikes before a saccade have preferred amplitudes and directions: Each of these neurons spikes strongest before a saccade with these properties and less strongly before different saccades.⇒
Moving the eyes shifts the auditory and somatosensory maps in the SC.⇒
If deep SC neurons are sensitive to tactile stimuli before there are any visually sensitive neurons, then it makes sense that their retinotopic organization be guided by chemical markers.⇒
There are at least polysynaptic pathways from deep SC to cortex.⇒
Kao et al. did not find visually responsive neurons in the deep layers of the cat SC within the first three postnatal weeks.⇒
Overt visual function can be observed in developing kittens at the same time or before visually responsive neurons can first be found in the deep SC.⇒
Some animals are born with deep-SC neurons responsive to more than one modality.
However, these neurons don't integrate according to Stein's single-neuron definition of multisensory integration. This kind of multisensory integration develops with experience with cross-modal stimuli.⇒
The deeper levels of SC receive virtually no primary visual input (in cats and ferrets).⇒
There are monosynaptic connections from the retina to neurons both in the superficial and deeper layers of the SC.⇒
Most of the multi-sensory neurons in the (cat) SC are audio-visual followed by visual-somatosensory, but all other combinations can be found.⇒