Journey to the Center of the Retina

Eyewire has hosted many competitions throughout the years, but surprisingly we’ve never done one that explores the subject of our entire citizen science project – the retina!

As we round the corner on our last sector of the Outer Realms, now seems like the perfect time to take a deeper look at the connectome that started it all!

What is the retina?

The retina is a layer of tissue at the back of the eye that captures light and sends signals to rest of the brain describing what it sees.

The retina is made up of 10 layers, and features 5 cell classes. You can check out groupings of cells that we’ve proofread in Eyewire in the Eyewire Museum.

Light’s journey through the retina begins with the photoreceptors (rods and cones), travels through the bipolar cells, and ends with the ganglion cells, which send axons out of the eye to various parts of the brain where the signals are received. Horizontal and amacrine cells act as “helpers” that mitigate the signal as it passes through.

Surprisingly, the photoreceptors are located at the very back of the eye, with the ganglion cells closest to the surface. This means light has to travel through the entire retina, hit the photoreceptors, and then signals are sent backwards up the cellular layers. This “inverted” retina is present in all vertebrates, but many invertebrates have their retinas the other way around, including cephalopods which have well developed eyes rivaling those of many vertebrates. Nature is pretty wacky sometimes!

Without further ado, let’s explore some of our retinal friends a bit further, and also win some points and badges! Let’s see what our competition has in store for us!

Photoreceptor Accuracy Happy Hours

First session runs from 8:00 AM to 10:00 AM on Thursday 6/19
Second session runs from 2:00 PM to 4:00 PM on Friday 6/20
Third session runs from 10:00 PM to midnight on Friday 6/20

Let’s dive right in at light’s first pitstop, the photoreceptors!

There are two types of photoreceptors — rods and cones — so named for the shapes of their respective outer segments. Rods activate in low light conditions and signal differences in light levels. They cannot detect color, which is why you may notice you can only see in shades of grey in extremely low-light conditions.

Cones become active under daytime conditions, and result in color vision. In persons with normal color vision, 3 types of cones are present. Signals at various points along the color spectrum active 1 or more cones. The combination of the signals these cone cells send result in a color output somewhere along the human visible light spectrum.

Mice are dichromatic, with just two types of cone cells, and see a much more limited color palette that lacks red detection. Red-green colorblind humans can relate!

Whether you enjoy the color accuracy of a cone cell, or the light contrast of a rod, let these photoreceptors inspire you to an amazing tracing accuracy during our Accuracy Happy Hours!

Bonuses:
1st Place Accuracy – 10,000 points
2nd Place Accuracy – 8,000 points
3rd Place Accuracy – 6,000 points
Achieve 95% Accuracy – 5,000 points
Achieve 90% Accuracy – 3,000 points
Achieve 80% Accuracy – 2,000 points
1,000 points for anyone under 80% who still plays at least 30 cubes in either slot.
(These bonus thresholds are non-cumulative, i.e. they will not combine. If you earn 3rd place, for instance, and presumably got over 95% accuracy, you still earn a 6,000 point bonus, not 11,000.)

Horizontal vs Amacrine Cells

Begins at 11:00 AM on Monday 6/23
Ends at 11:00 AM on Wednesday 6/25

Though they are not directly on the “train tracks” that light signals travel through to reach the brain, both horizontal and amacrine cells play essential parts in fine-tuning these signals as they flow through.

The first stop is the horizontal cells, which mitigate signals traveling between the photorecptors and the bipolar cells. These cells have neurites that act as both dendrites and axons, and send signals “horizontally” (hence the name). These inhibitory interneurons connect to multiple photoreceptor-to-bipolar junctions, and help neighboring cells co-regulate.

The next stop on the signal train is between the bipolar and ganglion cells, and there’s a helper cell guiding the signal along here as well – the amacrine cell! Like horizontal cells, these cell types are also inhibitory interneurons, and are important to the detection of directional movement.

Most amacrine cells live in the Inner Nuclear Layer (INL), though there are some present in the Ganglion Cell Layer (GCL) called “displaced” amacrine cells. The Starburst Amacrine Cell, an Eyewire fan favorite, is present in both these layers!

Which interneuron type are you? Pick your team and let the VS begin!

Bonuses:
Starting Lineup – top 3 players on each team, who earn 75% of their score in bonus points
All Other Players – earn 50% of their score in bonus points
Winning Team – 20,000 additional points
Each Team’s MVP – 5,000 additional points
(The winning team is determined by average points per player, with 2x weight given to Starting Lineup players. To qualify for any of the above bonuses or affect the team score, players must earn a minimum baseline of 2,000 points.)

Bipolar Cell Trivia

**Note: Trivia will be moving to a Power-Hour-only format**

Power Hour from 11:00 AM to 12:00 PM on Tuesday 6/24

Once light hits the photoreceptors, they send (or inhibit) the release of neurotransmitters to the next set of cells waiting down the line – the bipolar cells!

Bipolar cells are named for their shape – a soma with two sets of processes – one emerging from each “pole” of the cell body. They send different amounts of neurotransmitter depending on input signals, a process called “graded potential,” as opposed to the “all-or-nothing” action potential that most neurons send.

Thank your bipolar cells for helping bridge the gap in in the transmission of light signals as you study up for our trivia Power Hour!

Bonuses:
For every question —
1st to answer – 300 points
2nd to answer – 200 points
3rd to answer – 100 points

Ganglion Cell Marathon

Begins at 10:00 AM on Wednesday 6/25
Ends at 10:00 AM on Thursday 6/26

The last stop on the retinal signal train are the ganglion cells, which have their very own layer named after them, the Ganglion Cell Layer (GCL)!

These are specialized cells that play a pivotal role in signal processing before sending off their findings to various locations in the brain. There are over 40 types of ganglion cells!

The most studied classes of ganglions include parvocellular (P), magnocellular (M), and koniocellular (K), with parvocellular making up 70% of all ganglions. These various cell types make sense of things like spacial detail, color, motion, depth, contrast, and illumination.

Ganglions send out long axons through an area in the retina called the optic nerve, which then terminate in over 50 different brain regions! The “backwards” orientation of the retina means that the axon bundle has to intercept the entire retina, creating a blind spot at the location of the optic nerve. You brain generally compensates and “fills in” information for this blind spot, but you can discover it with this fun test!

Help us trace one (or more) cells in the final event of our competition – the Marathon! You’ll have 24 hours to complete the cell.

Bonuses:
One live cell will be designated the “marathon cell,” with a 3x points multiplier!
Cube count bonuses: 3500 points per cube traced.
SC bonuses are doubled on all cells.
Every 3 SCs counts for 1 cube toward naming eligibility & per-cell completion bonus.
50 cubes = 5,000 points per completed cell, plus rights to vote on a new name for the marathon cell
200 cubes = 10,000 points per completed cell, plus rights to nominate a new name for the marathon cell

Retina Closing Ceremony

Begins at 4:00 PM on Friday 6/27

Come celebrate the end of this competition, where admins will recognize everyone’s achievements. As always, we will include a round of promotions for Scouts, Scythes, Mystics, Moderators, and Mentors. If you’d like a promotion, you can request them here.